Potatoes Au Gratin with Guinness Cheddar Sauce

These Potatoes Au Gratin go into the oven thin-sliced and swimming in a Guinness cheddar sauce, and they come out with a top that's cracked and browned while the inside stays soft enough to cut with a spoon.

You might also like Scalloped Sweet Potatoes and Greek Hasselback Potatoes.

I call these Potatoes Au Gratin "sophisticated potatoes", because they look very presentable once out of the oven and usually show up for a special occasion, together with Grand Marnier Cranberry Sauce and Garlic Parmesan Sweet Potatoes.

🥔 Potatoes Au Gratin with Guinness Cheddar - Recipe Overview

✅ Prep Time: 20 minutes
🔥 Bake Time: 50 minutes
🍽️ Serves: 6-8
💲 Cost: About $12 total, roughly $1.75 per serving
👨‍🍳 Skill Level: Easy, but plan for real hands-on time
📦 Equipment: 12-inch cast iron skillet or baking dish, mandoline slicer, medium saucepan

These potatoes Au Gratin are thin-sliced russets or Yukon Golds bathed in a Guinness-spiked cheddar cream sauce, baked until the top turns deeply golden and the inside stays soft and saucy. The stout isn't a gimmick here - it pulls a malty, slightly bitter backbone through the cheese sauce that plain milk and cream can't touch on their own. Fresh thyme threads through every layer, and the whole thing bakes low and slow so the potatoes go fully tender instead of chalky in the center.

Why You'll Love This

• 🍺 Guinness does real work: the stout cuts through the richness of cheddar and cream so the dish reads as comforting instead of heavy.
• 🧀 Cheese in every layer, not just on top. Cheddar and Parmesan get folded into the sauce itself, so every forkful gets that pull - the exact reason this dish earns the "au gratin" name instead of a plain scalloped potato bake.
• 🕐 Make-ahead friendly: assemble it the night before, refrigerate, then bake - just add 10-15 extra minutes since it's going in cold.
• 🍽️ It pairs with almost anything. Roast chicken, baked pork chops, a simple green salad - this dish doesn't ask for much to look like the centerpiece.
• ⏱️ Less fuss than it looks. A mandoline gets you even slices in minutes, and the sauce comes together in one saucepan while the oven heats.
• 🎉 Built for the table that matters. I started making this version for the holidays when a plain potato bake felt too plain next to cranberry sauce and a glazed pork loin. It's stuck around every year since.

My mother-in-law used to bring a potato casserole to every family dinner, no cheese, no beer, just cream and butter, and it was fine. Good, even. But when I put Guinness in the sauce and watched the top brown up dark and blistered in the skillet, I knew I wasn't going back to fine.

A quick note on the name

Potatoes au gratin and scalloped potatoes get used interchangeably online, but there's a real difference: classic scalloped potatoes are cooked in a plain cream sauce with no cheese, while au gratin means cheese worked through the layers with a browned, crusty top. This recipe is cheese-forward from top to bottom, cheddar and Parmesan folded straight into the sauce, not just sprinkled on at the end, so au gratin is the more accurate name here. If you've been calling this dish scalloped potatoes your whole life, you're not wrong exactly, you're just using the wrong :).

What's In This?

• Potatoes: Russet potatoes give you that classic starchy texture, but Yukon Golds yield a creamier, saucier result. Both work - your choice!
• Cheese: Cheddar and Parmesan for extra cheesiness. Grate your own block cheese if you can. Pre-shredded works in a pinch, but it won't melt as smoothly into the sauce.
• Cream or Whole Milk: Heavy cream for the win. Whole milk will get you a lighter version, but the sauce won't cling to the potatoes the same way.
• Butter and flour - This is your roux, the base that turns milk and beer into an actual sauce instead of a puddle.
• Seasonings: Salt, pepper. I also used fresh thyme but you can also substitute with dried thyme. Fresh or dried rosemary works well tool
• Garlic: if you're a garlic lover, go ahead and add more than what the recipe calls for.

Essential Equipment

• Medium saucepan to cook cheese sauce in.
• Cast Iron Skillet or baking dish: I recommend to use 12 inch heavy skillet - it's large, but not too overwhelming.
• V-Blade mandoline slicer or this German engineered 5 ultra-sharp blade mandoline slicer. You want thin and evenly sliced potatoes here.

How to Make Guinness Potatoes Au Gratin

This is an overview with step-by-step photos. Full ingredients & instructions are in the recipe card below.

1. Prepare Cheese Sauce

1. Melt butter in a medium saucepan set over medium heat.
2. Add thyme and onion; cook 4 minutes or until onion is tender and golden, stirring occasionally.
3. Stir in flour, milk, cheese and salt. Cook, stirring constantly until slightly thickened.
4. Remove half of cheese sauce into a bowl.

2. Add Potatoes

Arrange potato slices, slightly overlapping, on top of the remaining sauce in the skillet

3. Top with Remaining Cheese

Pour the rest of the sauce on top of the potatoes. Potatoes Au Gratin prep work is done. Now for the oven time!

4. Bake

Potatoes Au Gratin for 45 minutes at 375 F. or until potatoes are tender. Remove from oven and top with remaining ½ cup cheese. Return to oven and bake, uncovered, 5 more minutes or until cheese is melted and bubbling.

Pro Tips

If using baking dish instead of the skillet: Before you add the potatoes to the buttered baking dish, you can pour a thin layer of milk (instead of the cheese sauce) into the bottom of the baking dish, so the bottom layer of potatoes will cook well and soak up the delicious goodness, like all the other layers.

How do I prevent The potatoes from curdling?

High heat can curdle cream or milk; bake at 350-375°F, use fresh dairy, and avoid overly acidic cheese varieties.

Why are My potatoes Au Gratin watery?

Too much moisture from potatoes or milk can cause watery results as well as slicing potatoes too thick or not baking long enough also prevents sauce from thickening.

Easy Fixes:

• Use starchy potatoes like Russet for better thickening.
• Pre-cook potato slices in milk or drain excess liquid before layering.
• Add a tablespoon of flour or cornstarch to the cream mixture to boost sauce consistency.

Why are my potatoes not fully cooked?

If you sliced your potatoes too thick - they will take longer to cook. Make sure to slice potatoes thinly using a mandolin and then bake covered to slow cooking and trap steam. Bake uncovered only for the final 15 minutes to allow browning.

Can I make Them Gluten Free?

Substitute flour with cornstarch or potato starch for thickening and ensure all ingredients are certified gluten-free.

What's the best way to reheat Them?

Cover leftovers with foil and reheat at 350°F until warmed through to maintain texture and moisture.

How do I make Them ahead?

Assemble and refrigerate up to 24 hours, then bake just before serving; add 10-15 minutes to bake time if baking cold from the fridge.

Substitutions and Variations

• If you can, shred your own cheese for the best outcome. Although pre-shredded is also good but you don't get that melting quality with the block.
• Use regular sized potatoes, since the little ones can be annoying to slice, even with a mandolin.
• You don't have to peel the potatoes, even though I did peel mine.
• Top the potatoes with breadcrumbs and melted butter for the last half of cooking. You can also add some onion powder and poultry seasoning to the cream mixture.

Serving Suggestions

Best main dishes to pair with potatoes au gratin are Garlic Mushroom Pork Chops, Oven Grilled Tandoori Chicken Skewers and Brown Sugar Dijon Glazed Pork Loin.

If you're making these for Christmas or Easter or Thanksgiving, try pairing with this Grand Marnier Cranberry Sauce and Ultimate Green Bean Casserole Skillet.

My top salad suggestions are Brussels Sprout Salad with Cranberries and Pecans and Blackberry and Avocado Salad.

Leftovers and Storage

• Potatoes Au Gratin will keep for 3-4 days in the fridge in a air-tight container to prevent moisture loss.
• Reheat in a covered saucepan on the stove at a low heat. You could also warm them up in the oven covered with foil if you've got a lot left still in the cast iron skillet or casserole dish.
• I wouldn't recommend freezing leftovers because of the cheese and cream.

More Easy Potato Recipes

• Instant Pot Cheesy Garlic Mashed Potatoes
• Southern Potato Salad with Mustard, Eggs and Pickles
• Buttery Mashed Potato Pie with Herb and Garlic Cream Cheese
• Irish Mashed Potatoes with Bacon (Colcannon)

This recipe was originally published in 2018. Since then I improved the structure of the recipe, added several helpful sections as well as updated the photos, but the recipe stayed the same.