Preheat the oven to 400°F. Line a baking sheet with parchment paper and set aside. Wash and slice the bottoms off of 2 lbs Brussels sprouts. Peel off the outer layer of each one, then slice them in half.
In a large bowl, mix together ¼ cup olive oil, 3 minced garlic cloves, 1 tsp salt and ½ tsp ground black pepper.
Add the 2 lbs sliced Brussels sprouts to the bowl and toss them with the sauce until evenly coated.
Spread the brussels sprouts onto the baking sheet in a single layer. Bake for 30-35 minutes, tossing halfway through, or until edges are crispy and also soft inside when poked with a fork.
While the Brussels sprouts are baking, add ½ cup balsamic vinegar, ¼ cup honey, 2 Tbsp brown sugar, 1 Tbsp dijon mustard and ½ tsp red pepper chili flakes to a saucepan. Bring this to a simmer over medium heat, while stirring slowly but constantly. Let simmer until the sauce has thickened to a syrup consistency, about 10 minutes.
Add the Brussels sprouts to a large serving dish and drizzle the balsamic sauce overtop. Sprinkle with freshly grated parmesan cheese (optional). Serve and enjoy.