3 cups coarse fresh bread crumbs
3 Tbsp. unsalted butter, melted
1 1/2 tsp. lemon zest
1/2 tsp. kosher salt
1/2 tsp. freshly ground pepper
2 Tbsp. minced fresh flat-leaf parsley
For the Gratin:
1 Tbsp. unsalted butter
Kosher salt to taste, plus 2 tsp.
2lb brussels sprouts, trimmed and halved lengthwise
2 Tbsp all purpose flour
8 oz Gruyere cheese, grated
1 oz Parmigiano- Reggiano, grated
1 tsp lemon zest
3/4 tsp freshly ground pepper
1 cup heavy cream
1 jar caramelized shallots, liquid drained
Preheat an oven to 375º. Grease a ovenproof casserole dish. To make topping, in a bowl, stir together the bread crumbs, butter, lemon zest, salt, pepper and parsley. Set aside
Bring a large pot of salted water to a boil over high heat. Add the brussels sprouts and cook until tender, 5-7 minutes. Drain, then transfer to bowl of ice water.. Drain and pat dry with paper towels.
To make gratin, in bowl, stir together the flour, Gruyere, Parmigiano-Reggiano, lemon zest, the 2 tsp. salt and the pepper. Stir in the cream, then the brussels sprouts and caramelized shallots. Transfer mixture to casserole dish and sprinkle with bread crumb mixture. Bake until golden brown and gratin is bubbly about 35 minutes. Let the gratin cool for 15 minutes before serving.