Preheat the oven to 350 degrees F.
Place the prosciutto slices on a baking sheet and bake until just crisp
, about 10 minutes. Let cool. Crumble the prosciutto slices into a container and store in the refrigerator.
In a blender, combine the orange zest
, orange juice
, balsamic vinegar
, garlic, salt, and pepper. Blend until smooth. With the blender
running, add the olive oil in a steady stream until combined. Transfer to a container and store in the refrigerator.
To serve, put the spinach
in a large bowl. Toss with enough of the vinaigrette
to coat the spinach. Sprinkle with the crisp prosciutto
crumbles, toss again, and serve.