Step 1: Heat olive oil in a skillet. Add shallots and cook until transparent. Add spinach, garlic, and dill. Cook until spinach has wilted and garlic is fragrant.
Step 2: In a large bowl, mix the spinach mixture with bacon, cream cheese, feta, one egg yolk, and salt and pepper.
Step 3: Roll the puff pastry dough out and cut into 12 squares. Place each square in a cup of the muffin tin.
Step 4: Fill each cup with a rounded tablespoon of the spinach mixture.
Step 5: Pinch the corners of the pastry squares together. Mix the remaining egg and egg white together and brush over each pastry.
Step 6: Bake at 450 for 25 minutes. Serve hot.