Preheat oven to 400°F (200°C). Toss sprouts with oil, salt, and pepper. Roast 20–30 minutes until golden, flipping halfway.
Fry bacon in a pan until crisp. Remove bacon, leaving 1 tbsp drippings.
Add butter, sauté onion 5–7 minutes, then garlic 1 minute.
Stir in flour, cook 1 minute. Whisk in milk, mustard, miso, parmesan. Simmer 3–5 minutes until thickened.
Fold roasted sprouts and bacon into sauce. Season, garnish with cheese.
Serve warm for a flavorful side dish.
