Preheat your grill to medium-high heat.
Season chicken breasts with salt & pepper. In a small bowl, whisk together balsamic vinegar, olive oil, honey, & minced garlic. Pour marinade over chicken breasts & let them marinate for at least 30 minutes.
Set up three shallow bowls: one with flour, one with beaten egg, & one with breadcrumbs. Dredge each slice of goat cheese in flour, then dip in the beaten egg, & finally coat it with breadcrumbs. Heat oil in a skillet over medium heat & fry coated goat cheese slices until golden brown & crispy on both sides. Remove from skillet & set aside on paper towels to drain excess oil.
Grill marinated chicken breasts for 6-8 minutes on each side, or until they are cooked through & have grill marks. Remove from grill & let them rest for a few minutes before slicing them thinly.
Whisk together balsamic vinegar, olive oil, honey, salt, & pepper in a small bowl.
In a large salad bowl, combine mixed greens, blackberries, raspberries, sliced avocado, chopped walnuts, & thinly sliced red onion.
Drizzle balsamic vinaigrette over the salad & toss until everything is evenly coated.
Divide salad onto serving plates, top each portion with sliced grilled chicken, & garnish with crispy fried goat cheese rounds.