Cheesy Potato Gratin

Ingredients:
1 Tbs. unsalted butter
1 shallot, finely chopped
2 Tbs. all-purpose flour
1/2 cup chicken stock
1/2 cup heavy cream
1 cup grated Gruyère cheese
1 tsp. chopped fresh thyme
Salt and freshly ground pepper, to taste
3 lb. Yukon Gold potatoes, peeled and cut into 1 1/2-inch chunks
1/2 cup grated Parmigiano-Reggiano cheese
Directions:
Preheat an oven to 375ºF.

In a 10-inch nonstick fry pan over medium heat, melt the butter. Add the shallot and cook, stirring occasionally, until tender, 3 to 4 minutes. Add the flour and cook, stirring constantly, until fragrant, 1 to 2 minutes. Slowly stir in the stock and cream. Add the Gruyère and thyme and stir until the cheese has melted, about 1 minute. Season with salt and pepper. Add the potatoes and stir to coat them well. Cover the pan and cook over medium heat for 15 minutes.

Remove the lid and sprinkle the Parmigiano-Reggiano on top. Transfer the pan to the oven and bake, uncovered, until the top is golden brown and bubbling at the edges, 30 to 35 minutes. Let cool for 5 minutes before serving. Serves 6 to 8.