Caramelized onions cooked down into a rich gravy with hasselback Yukon gold potatoes placed on top, then baked with Gruyère and parmesan until deeply golden. Savory and cheesy with classic French onion flavor.
0 Caramelize the Onions: Heat a large skillet over medium heat for about 2 minutes. Add a drizzle of olive oil, then add the onions and shallots. Caramelize for about 40 minutes, stir often and deglaze with 2 tbsp water as needed. Add the salt, nutmeg, thyme, and balsamic vinegar, then continue cooking for another 20 to 30 minutes until deeply golden.
1 Build the Onion Gravy: Push the onions to one side of the skillet. Add the butter to the empty side and let it melt. Sprinkle in the flour and stir into the butter for about 3 minutes. Gradually stir in 2 cups of beef broth, adding as much of the remaining broth as needed till you reach a thickened consistency. Remove from heat.
6 Prepare the Potatoes: Using a sharp knife, cut each potato in a hasselback style. See notes for optional help on how to do this. In a small bowl, mix the olive oil, garlic powder, onion powder, white pepper, and a pinch of salt. Brush the mixture generously over and between the slices of the potatoes.
3 Assemble: Preheat the oven to 400°F. Spread the onion gravy evenly in a baking sheet and sprinkle half of the cheeses on top. Arrange the potatoes, flat side down, in straight lines on top of the onion gravy and top with the remaining cheeses.
4 Bake: Cover the dish tightly with foil and bake 40 minutes. Remove the foil, increase the oven temperature to 425°F, and bake for another 20 to 30 minutes until the potatoes are tender and the top is deeply golden.
5 Finish and Serve: Top with more parmesan, chopped chives, and black pepper and that's it.
