Step 1: Season the chicken - Start by seasoning both sides of the chicken breasts with salt, black pepper, and Italian seasoning. This is where the flavor begins, so take a second to coat them evenly. Place the seasoned chicken directly into the slow cooker.
Step 2: Build the sauce - Sprinkle the minced garlic over the chicken. Pour the drained diced tomatoes and balsamic vinaigrette dressing over the top. If you are using sugar, sprinkle it in now to help balance the acidity of the tomatoes.
Step 3: Slow cook - Cover the slow cooker and cook on Low for 6 hours or on High for 3 hours. The chicken should be tender, cooked through, and easy to cut with a fork.
Step 4: Add the cheese - Once the chicken is cooked, sprinkle the shredded mozzarella evenly over the top. Cover again and let it sit for about 10 minutes until the cheese is melted and gooey.
Step 5: Make the bruschetta topping - While the cheese melts, combine the halved cherry tomatoes, chopped basil, olive oil, balsamic vinaigrette, and a pinch of salt and pepper in a small bowl. Gently toss everything together.
Step 6: Finish and serve - Spoon the fresh bruschetta mixture over the cheesy chicken just before serving. This final step adds freshness and color that really makes the dish shine.