Preheat oven to 425 degrees. Line two sheet pans with parchment paper or tin foil.
To prepare your glaze, place vinegar, honey, butter, and garlic in a saucepan. Bring to a boil, then decrease the heat to a simmer. Cook for about 8-10 minutes or until glaze has reduced and has slightly thickened.
While the glaze is cooking, place Brussels sprouts in a large pan and cover them with water. Bring to a boil and cook for 10 minutes. Drain off water, then toss with oil, salt, and pepper.
Place half of the sprouts on each sheet pan. Using a heavy jar, glass, or coffee cup, smash each one down to flatten.
Place trays in the preheated oven and bake for 10 minutes.
Remove Brussels sprouts from the oven and spoon glaze on top of each sprout. Place back into the oven and continue roasting for an additional 10, or until the bottoms are crispy.