Brown Butter Sage Potato Gratin

Brown Butter Sage Potato Gratin turns a familiar potato side into something special without making dinner complicated. Thin slices of Yukon Gold potatoes bake in a warm cream sauce with garlic, nutty browned butter, and fresh sage. Parmesan adds savory richness between the layers and a beautifully golden finish. Just before serving, crispy shallots bring a delicate crunch.

The ingredient list is simple, but the flavors feel wonderfully layered. A mandoline makes the slicing quick, while the oven does most of the work. Meanwhile, the shallots turn golden on the stove and become crisp as they cool.

After a short rest, the creamy sauce settles around the tender potato slices, making the gratin easy to serve. It’s a lovely choice for Thanksgiving, Christmas, or a dinner that deserves an extra-special side. And those golden shallots? They’re worth adding at the very last moment.

Recipe Yield: 8 servings

INGREDIENTS

2 1/2 lbs Yukon Gold potatoes, peeled and thinly sliced (about 1/8 inch)
5 tbsp unsalted butter, divided
1 1/2 cups heavy cream
1/2 cup whole milk
3 garlic cloves, minced
3/4 cup finely grated Parmesan cheese, divided
2 medium shallots, thinly sliced into rings (about 1/16 inch)
8 fresh sage leaves, divided
3/4 tsp fine sea salt
1/2 tsp freshly ground black pepper
1/8 tsp ground nutmeg
1/2 cup neutral oil, such as avocado or canola, for frying

INSTRUCTIONS

1. Prepare the oven:
Preheat the oven to 375°F. Lightly grease a 9-inch square or 11×7-inch rectangular baking dish with 1 tbsp butter.

2. Slice the potatoes:
Wash and peel the Yukon Gold potatoes. Slice into even 1/8-inch rounds using a mandoline or sharp knife. Do not rinse the slices, as their natural starch helps thicken the sauce.

3. Brown the butter:
Melt the remaining 4 tbsp butter in a medium saucepan over medium heat. Swirl occasionally for 3–5 minutes, until golden brown and nutty. Remove from the heat immediately.

4. Prepare the cream sauce:
Add the heavy cream, milk, garlic, 4 finely chopped sage leaves, salt, pepper, and nutmeg. Warm over medium-low heat for 2–3 minutes, stirring gently without boiling.

5. Layer the potatoes:
Arrange one-third of the potatoes in overlapping layers in the prepared dish. Pour over one-third of the warm cream mixture and sprinkle with one-third of the 1/2 cup Parmesan reserved for layering. Repeat twice, finishing with cream.

6. Bake the gratin:
Cover snugly with a fitted oven-safe lid or an inverted baking sheet. Bake for 55–65 minutes, until the potatoes are nearly tender when pierced with a thin knife. Continue baking covered if needed.

7. Brown the top:
Remove the cover and sprinkle with the remaining 1/4 cup Parmesan. Bake uncovered for 15–25 minutes, until golden and bubbling. A knife should slide easily through the center.

8. Crisp the shallots:
While the gratin finishes baking, add the shallot rings and oil to an unheated small saucepan. Cook over medium-low heat for 15–25 minutes, stirring often, until lightly golden. Remove with a slotted spoon and drain on paper towels. The shallots will crisp as they cool.

9. Prepare the sage garnish:
Finely chop or tear the remaining 4 fresh sage leaves into small pieces. For a crispy alternative, fry the whole leaves in the hot shallot oil for 10–20 seconds, then drain and crumble once cooled.

10. Rest and garnish:
Let the gratin rest for 15 minutes so the creamy layers settle. Scatter the crispy shallots and prepared sage evenly over the top just before serving.

Helpful Tips to Perfect This Recipe

• Slice the potatoes evenly: Aim for consistent 1/8-inch slices so every layer becomes tender at the same time. Keep the natural starch by avoiding rinsing.
• Watch the browned butter: Butter can go from golden to burnt quickly. Remove it from the heat as soon as the milk solids turn amber and release a pleasant nutty aroma.
• Check the center before serving: The golden top doesn’t always mean the potatoes are fully cooked. Insert a thin knife into the middle. If you feel resistance, continue baking until tender.
• Perfect the crispy shallots: Slice them thinly and remove them when lightly golden, before they turn dark. They’ll continue browning briefly and become crisp as they cool. Add them just before serving.
• Prepare ahead for the holidays: Bake the gratin up to 1 day ahead and refrigerate within 2 hours. Reheat covered at 350°F until the center reaches 165°F, then uncover briefly to restore the golden top. For the best crunch, prepare the shallots fresh.