Preheat the oven to 400 F. Heat a small (8") cast iron pan over medium heat. Cook chopped bacon in the pan until crispy. Transfer the bacon to a plate lined with paper towels and set aside, leaving the rendered bacon fat in the pan.
While the bacon is cooking, cut the ends off of each brussels sprout and discard. Thinly slice the brussels sprouts (into "shreds"), and set aside.
Cook the shallots in the bacon fat for 2-3 minutes until browned and softened, then stir in the garlic and cook for 30 seconds.
Add the thinly sliced (shredded) brussels sprouts to the skillet, stirring/tossing them with the bacon fat, shallots, and garlic for 3-4 minutes until tender.
Sprinkle in the nutmeg, mustard powder, and a pinch of salt, then continue stirring/tossing the brussels sprouts frequently for another 3-4 minutes so the brussels sprouts continue to soften.
Stir in the vegetable stock, cook for 1-2 minutes until mostly absorbed, then stir in the heavy cream. Cook for another 2-3 minutes until the cream is mostly absorbed.
Stir in 1/2 cup of shredded gruyere cheese, followed by the crispy chopped bacon.
Squeeze a lemon wedge over the dish, then stir in the lemon juice along with a pinch of salt and a few cracks of fresh black pepper.
Top the dish with the remaining 1/4 cup of gruyere cheese and all of the parmesan cheese.
Cook in the 400 F oven for 8-10 minutes until the cheese is melted and bubbly, then switch the oven to a "high" broil, and broil for 2-3 minutes until the cheese starts to brown. Serve hot! (Pan will be very hot, so be careful!)
Nutrition
Serving: 1servingCalories: 436kcal
Keyword brussels sprouts gratin, brussels sprouts recipe with bacon