Heat oven to 375°F. Spray 12 regular-size muffin cups with cooking spray. In medium bowl, mix potatoes, spinach, cheese, butter, salt and pepper.
Unroll 1 can of dough; separate into 8 triangles. Press each into muffin cup to form cup. Unroll second can of dough; remove 4 triangles and press each into muffin cup to form cup. Fold tails of triangles over and press into cups. (Reserve remaining 4 triangles for a future use; refrigerate.)
Divide potato mixture evenly into dough-lined muffin cups.
Bake 12 to 13 minutes or until crusts are light brown. Serve warm.