To make the salad: Combine the fennel, peas, pea shoots, sunflower seeds, and garlic in a bowl.
Make the dressing by combining the ingredients in a bowl and whisking together. Pour the dressing over the fennel mixture and let sit while finishing the salad.
Toss together the cubed bread, olive oil, salt, and pepper. Spread into a single layer on a sheet tray and bake until crisp, 12 to 14 minutes. Remove from the oven and cool slightly.
Fold the toasted bread into the fennel mixture and serve over the spinach.
Notes
+ If you can't find garlic scapes, use a couple chopped scallions.