3 Tbs unsalted butter, plus more for coating dish
5 Tbs finely grated Parmesan cheese, divided
1 cup (250 mL) whole milk
3 Tbs all-purpose flour
½ tsp paprika
½ tsp dry mustard powder
½ tsp salt
Pinch ground nutmeg
5 large egg yolks
5 large egg whites
½ tsp cream of tartar
½ cup shredded aged cheddar
½ cup grated Gruyère cheese
2 Tbs chopped fresh dill
- Preheat oven to 400º F and place a baking sheet on the lowest rack. Generously butter a 1.5 L soufflé dish. Coat the bottom and sides with 3 Tbs Parmesan cheese, tapping out any excess.
- In a small pot, heat the milk until steaming. Meanwhile, melt the butter in over medium heat. Whisk in the flour and cook for 3 minutes, stirring constantly. Remove from the heat and whisk in the warm milk. Return the skillet to the heat and cook until thickened and smooth, whisking constantly, about 3 minutes.
- Remove the skillet from the heat and whisk in paprika, dry mustard, salt and nutmeg. Whisk in the egg yolks one at a time, blending well after each addition. Transfer the flour and yolk mixture to a large bowl.
- Using an electric mixer or a stand mixer fitted with a whisk attachment, beat the egg whites and cream of tartar at medium speed until the mixture holds stiff peaks. They should still be glossy and not dry.
- Fold a quarter of the whites into the barely warm yolk mixture to lighten. Gently fold in remaining whites in two additions while gradually sprinkling in the cheddar, Gruyère, remaining 2 Tbs Parmesan, and the dill. Transfer the batter to the prepared dish. Rub your thumb around the inside edge of the dish to create a 5 mm or so space between the dish and the soufflé mixture.
- Place the dish on the baking sheet in the oven and reduce temperature to 375º F. Bake until soufflé is puffed and golden brown on top and the centre barely jiggles when dish is shaken gently, about 30 minutes. Serve immediately.