Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper to prevent sticking.
Pat the chicken breast dry with paper towels and cut it into 1-inch bite-sized pieces for even cooking.
Clean the cremini mushrooms with a damp cloth and slice them in half, or leave them whole if they are small.
In a large mixing bowl, combine the chicken pieces, mushrooms, minced garlic, and fresh thyme leaves.
Drizzle the olive oil and balsamic vinegar over the mixture, then sprinkle with the sea salt and black pepper.
Toss all ingredients thoroughly until the chicken and mushrooms are well-coated with the oil and aromatics.
Spread the mixture in a single layer on the prepared baking sheet, ensuring there is space between the pieces to allow for proper roasting.
Roast for 18 to 22 minutes until the chicken reaches an internal temperature of 165°F and the mushrooms are tender and caramelized.
Remove from the oven and garnish with fresh chopped parsley before serving immediately.