Prepare the base by placing fresh baby spinach in a large mixing bowl.
Add thinly sliced red onions and fresh blackberries to the greens.
Season the pre-cooked grilled chicken breast with salt and pepper, slice into strips, and incorporate into the mixture.
Sprinkle crumbled goat cheese and chopped toasted walnuts evenly over the top.
Whisk together extra virgin olive oil and balsamic glaze in a separate small container.
Drizzle the dressing over the salad and toss gently to ensure even distribution.
Transfer to plates and serve immediately.