Preheat oven to 425°F and set a baking sheet to the side.
Trim the ends of the Brussels sprouts and then cut in half. Remove any flimsy leaves if necessary. (I like roasting the leaves that go rogue, they are like addicting little chips after they get roasted!)
2 1/2 lb. Brussels sprouts
Toss Brussels sprouts in a large bowl with olive oil, 1 tsp. salt and black pepper until lightly and evenly coated.
1/3 cup olive oil, 1 1/2 tsp. kosher salt, divided
Arrange Brussels sprouts, cut side down, on a baking sheet (use 2 baking sheets if needed if Brussels seem crowded). Roast in oven for ~20 minutes. They should be tender and deeply golden. Be sure not to flip Brussels while roasting.
Meanwhile make the honey balsamic sauce. Heat honey in a saucepan over medium-high heat until it honey begins to bubble, about 1-2 minutes.
1/3 cup honey
Remove from heat and add in balsamic, Dijon, garlic, chili flakes, and the remaining 1/2 tsp. salt.
1/3 cup balsamic vinegar, 1 Tbsp. Dijon mustard, 2 cloves garlic, minced, 1 tsp. red pepper chili flakes
Return to medium-low heat, add the butter and cook until sauce thickens. About 5 additional minutes.
3 Tbsp. butter, unsalted
Spoon glaze over roasted Brussels and toss to coat or serve sauce on the side. Garnish Brussels with lemon zest and green onions, if desired. Enjoy!
garnish: green onions and lemon zest