Ingredients:
1 Tablespoon mustard, dry
|
Directions:
1. Preheat the oven to 375°F. Rub the inside of a 2-quart casserole with butter.
2. Melt 3 tablespoons of the butter in a 4-quart Dutch oven over medium heat. Add the onions, garlic, and a pinch of salt and cook until very soft and translucent, about 15 minutes. Add the cream and bring the mixture to a simmer. Cut the heat down to low and cook until the cream is slightly thickened, about 5 minutes.
3. Meanwhile, thinly slice the Brussels sprouts crosswise on a mandoline, slicing just until you get to the hard core; reserve the rest of the sprouts for another use. Or, if you have a 2mm slicing disk for your food processor, you can carve out the hard core of the Brussels sprouts and then process the sprouts through the feed tube. You should end up with about 14 cups of thin, coleslaw-like rounds.
4. Melt another 2 tablespoons of the butter in a small skillet over medium heat. Stir in the flour and cook, stirring constantly, just until the mixture begins to smell toasty, about 2 minutes.
5. Mix the mustard with 1 tablespoon of water to make a thin paste. Whisk 2 tablespoons of the flour-butter mixture into the onions along with the mustard paste, nutmeg, and 2 teaspoons salt; crank the heat up to medium and continue whisking until the mixture comes to a simmer and begins to thicken, about 2 minutes. Cut the heat to low and cook until the sauce loses any floury taste or grainy texture, about 10 minutes.
6. Fit a food processor with the metal blade, and add the panko, Parmesan, 1 teaspoon salt, ½ teaspoon lemon zest, and the remaining 6 tablespoons butter. Process to a crumbly paste. Spread the crumb mixture on a sheet of parchment paper or plastic wrap, top with another sheet, and, using a rolling pin, roll the crust to fit the top of the casserole.
7. Carefully pour the onion sauce into a blender and blend until smooth. Add the remaining zest from the lemon, all of the lemon’s juice, and 1 teaspoon salt. Blend again until smooth. Pour the sauce back into the pot and fold in the sliced Brussels sprouts. Bring the mixture to a gentle simmer and cook until the sprouts are wilted, about 5 minutes.
8. Spoon the mixture into the prepared casserole. Remove the top sheet from the panko crust and invert over the Brussels sprouts.
Remove the other sheet and bake until golden brown and bubbly, about 40 minutes. Serve hot.
Prep Ahead Tip/ You can make and puree the sauce, slice the Brussels sprouts, and make and roll out the topping ahead of time and refrigerate them. Then just reheat the sauce, fold in the Brussels sprouts, assemble, and bake. Once you assemble the dish, it should be baked right away. If the Brussels sprouts sit in the sauce for too long before baking, they will lose their delicate flavor and texture. |
