Combine first 9 ingredients in a small bowl, stirring with a fork until blended. Set aside.
Remove and discard stems from spinach leaves. Bring water to a boil in a small saucepan. Cook spinach leaves, one at a time, in boiling water 15 seconds. Place leaves on paper towels to drain.
Coat 4 (1 3/4-inch) miniature muffin pan cups with cooking spray. Line each cup with a spinach leaf, covering bottom and sides of cup, allowing leaf to overhang. Spoon cheese mixture evenly onto spinach leaves. Fold leaves over to enclose cheese mixture. Bake at 350° for 20 minutes. Carefully remove from pan. Serve warm.