Few recipes are as comforting as a classic French Onion Soup. The sweet caramelized onions, hint of Cognac, toasty croutons, and melty cheese—it’s a winning combination. With these ingredients in mind, we created the French Onion POPOVER. Think airy popovers with a cheesy top and a caramelized onion butter that melts into the pillowy bread. These popovers would be great alongside homemade soup or with your holiday prime rib!
Butter In a medium skillet, melt 2 tablespoons of the butter. Add the onion and a ¼ teaspoon of salt. Cook over moderate heat, stirring occasionally, until golden brown, about 25 minutes. (If the onion begins to stick, add a splash of water. If they start to darken too quickly, lower the heat.) Add the Cognac, if using, and cook until evaporated, about 2 minutes. Let the onions cool completely.
In a medium bowl, mix the caramelized onions with the thyme leaves, lemon zest and the remaining 2 sticks of softened butter until combined. Season with salt and pepper. Spoon the butter onto a ramekin. If not using right away, refrigerate the butter. Bring to room temperature before serving.
Make the Popovers
Set a 6-cup popover pan on the bottom rack of the oven (leaving ample room between the pan and the rack above it). Preheat the oven to 450°F.
In a small bowl, combine the parmesan and Swiss cheeses.
In a small saucepan, warm the milk until small bubbles begin to form around the edges. In a medium bowl, whisk the eggs until they look frothy. While whisking constantly, gradually stream in the warm milk, being careful not to let the eggs cook. Whisk vigorously until small bubbles appear. Using a fine mesh sieve, sift the flour and salt into the bowl and whisk until smooth.
Remove the popover pan from the oven and coat the cups with nonstick spray. Fill the prepared cups three-quarters of the way with the popover batter and sprinkle the cheese mixture on top (about 1 heaping tablespoon per popover).
Return the pan to the oven and bake for 20 minutes. Rotate the pan 180 degrees and then reduce the oven to 350°F. Continue baking until the popovers are golden brown and puffed, 15 to 20 minutes more. Do not open the oven after rotating the pan.
Invert the popovers into a wire rack and prick each one with the tip of a paring knife to let the steam escape (this helps the popovers stay crunchy!). Serve right away, passing the French onion butter at the table.
NOTE This recipe can be easily doubled. If so, double the batter and bake in two batches. After baking your first batch, use a paper towel to wipe out the popover cups, then return the pan in the oven for 5 to 10 minutes. Repeat the baking process with the remaining popover batter. This recipe makes enough French onion butter for 12 popovers.