Rinse and dry the Brussels sprouts. Cut each one in half and remove any damaged leaves. Toss with olive oil, salt, and pepper. Preheat the oven to 360°F (180°C).
Spread them on a baking tray lined with parchment paper. Add thyme on top. Roast for 20 minutes, until softened but still firm inside.
While the sprouts are roasting, heat the remaining oil in a pan. Cook the onion for 5 minutes, until soft. Add garlic and cook for 1 more minute.
Add sliced bacon to the pan. Fry for 7–8 minutes, stirring occasionally, until lightly golden.
Remove from the oven and check for doneness — they should be tender but not mushy, about al dente texture.
Transfer the Brussels sprouts to a large bowl. Add the cooked bacon, onions, and garlic.
Mix well. Transfer to a serving plate and drizzle with balsamic glaze. Add extra thyme if desired. Serve warm.