Preheat your oven to 400°F (200°C).
Clean and halve the mushrooms.
In a bowl, toss the mushrooms with olive oil, minced garlic, thyme, salt, and pepper.
Spread the mushrooms on a baking sheet in a single layer.
Roast for 15-20 minutes, stirring halfway through, until golden and tender.
While the mushrooms roast, heat balsamic vinegar in a small saucepan over medium heat. Bring to a simmer and cook until it reduces by half (about 5 minutes). Add honey for sweetness, if desired.
Once the mushrooms are done, drizzle the balsamic reduction over them and serve.