Perfect Au Gratin Potatoes (No Par-Boiling Required!)
If you’re looking for perfectly creamy au gratin potatoes with a golden, cheesy crust, this is the recipe you’ll come back to again and again. These potatoes are rich, comforting, and cooked to absolute perfection — no par-boiling needed.
The secret? Ultra-thin, evenly sliced potatoes made with a rotary cheese grater, plus a luxurious homemade cheese sauce that coats every slice. The result is a dish with the ideal cheese-to-potato ratio, a gooey interior, and a crisp, irresistible cheese crust on top.
Whether you’re serving these for a holiday, Sunday dinner, or special occasion, this au gratin potato recipe never disappoints.
Why This Au Gratin Potato Recipe Works
Many au gratin recipes require boiling the potatoes first, which adds time and extra dishes. This method skips that step entirely by slicing the potatoes thin enough to fully cook in the oven.
Using a rotary cheese grater ensures:
- Even potato thickness for consistent cooking
- Faster prep time
- Perfectly grated cheese that melts smoothly into the sauce
Every detail in this recipe is intentional — from when the cheese is added to how long the dish rests before serving.
Ingredients for Perfect Au Gratin Potatoes
Potatoes
- Thinly sliced potatoes (cut with a rotary cheese grater)
Cheese Sauce
- Butter
- Diced onion
- Minced garlic
- Flour or cornstarch (for a gluten-free option)
- Whole milk
- Heavy whipping cream
- Salt and pepper
- Freshly chopped thyme leaves
- Freshly grated extra sharp Parmesan cheese
Topping
- Grated Gruyère cheese
- Parmesan cheese
Pro tip: Grate all cheese fresh using the rotary cheese grater for the smoothest sauce and best melt.
How to Make Au Gratin Potatoes (Step-by-Step)
1. Slice the Potatoes
Use a rotary cheese grater to slice the potatoes thin and uniform. This guarantees they cook fully in the oven without par-boiling.
2. Make the Cheese Sauce
In a saucepan, melt the butter and sauté the diced onion until soft. Add the minced garlic and cook just until fragrant.
Whisk in the flour (or cornstarch), then slowly add the milk and heavy cream. Season with salt, pepper, and fresh thyme. Stir until thickened, then melt in the freshly grated extra sharp Parmesan cheese.
The sauce should be rich, creamy, and smooth.
3. Assemble & Bake (Covered)
Toss the potatoes in the cheese sauce, making sure everything is well coated. Add to a buttered 9×13 dish, cover tightly with foil and bake for 1 hour.
This slow bake allows the potatoes to become perfectly tender while absorbing some of the sauce.
The Secret to the Perfect Cheese Crust
After the first hour of baking, remove the foil and add the cheese topping.
Sprinkle the Gruyère and Parmesan over the potatoes and return the dish to the oven uncovered for 20 minutes. Finish with a quick broil to achieve a golden, bubbly crust.
Adding the cheese later prevents it from melting into the potatoes — instead, it forms a divine, crispy cheese layer on top.
Make-Ahead Au Gratin Potatoes (Perfect for Holidays)
This recipe is ideal for prepping ahead of time.
To Make Ahead:
- Follow the recipe through the first hour of covered baking
- Remove from the oven and cool to room temperature
- Cover and refrigerate overnight
To Finish:
- Remove from the refrigerator 1 hour before baking
- Top with Gruyère and Parmesan
- Bake uncovered for 20 minutes on the top rack
- Broil for color
Let Them Rest (Don’t Skip This!)
Once baked, let the au gratin potatoes rest for 30 minutes before serving.
This allows the sauce to set slightly, giving you:
- Creamy, gooey cheese sauce
- Perfectly cooked potatoes
- Clean slices with incredible texture
Final Thoughts: The Perfect Au Gratin Potatoes
These perfect au gratin potatoes are everything the dish should be:
- Creamy and rich
- Perfectly cooked without par-boiling
- Gooey inside with a crisp cheese crust
- Balanced with fresh thyme and sharp Parmesan
If you’re looking for a foolproof, show-stopping potato side dish, this recipe delivers every single time.
Perfect Au Gratin Potatoes
Ingredients
- 2 lbs yukon gold potatoes thinly sliced
- 3 tbsp salted butter
- 1/2 medium yellow onion diced
- 2 cloves of garlic minced
- 3 tbsp flour
- 2 c whole milk
- 1/2 c heavy whipping cream
- 2 tsp kosher salt
- 1/2 tsp pepper
- 1/2 tsp fresh thyme leaves minced
- 8 oz extra sharp cheddar cheese freshly grated
Topping
- 8 oz gruyere cheese shredded
- 2 tbsp parmesan cheese grated
Instructions
- Preheat oven to 375 degrees
- Thinly slice potatoes. Set aside.
- Shred extra sharp cheddar cheese and set aside.
- To a pan over medium heat melt butter and cook diced onion for 10 minutes.
- Add minced garlic and cook one more minute before adding flour. Whisk the flour and cook the raw taste out for at least a minute before adding the whole milk and heavy whipping cream. Whisk the lumps out.
- Add salt, pepper, fresh thyme. Whisk well then add the shredded extra sharp cheddar cheese in batches. Whisk until melted before adding more.
- Dry off the potato slices if they excreted water. Toss in the cheese sauce.
- Place the cheesy potatoes in a buttered 9x13 dish or pan and cover with foil.
- Bake for one hour uncovered.
- If making ahead of time, remove from the oven and allow to cool completely to room temperature. Cover and refrigerate. Continue with the next step when ready to serve. Remove from the refrigerator an hour before baking so the pan loses it's chill.
- Remove the foil, add the shredded Gruyere and parmesan cheese. Put back in the oven on the top shelf. Bake uncovered for 20 minutes until the cheese is melted. Broil at the end until the top is golden brown.
- Allow to rest for 20 minutes before serving.