Spinach & Cheese Triangles

Name: Spinach & Cheese Triangles
Cuisine: European, Mediterranean
Ingredients: 3 sheets reduced-fat puff pastry (cut into four square pieces each); 2 cups baby spinach leaves; 1 brown onion (peeled); 2 cloves garlic (peeled); 1/2 cup reduced-fat ricotta cheese; 1/2 cup reduced fat feta cheese; 1 lemon (juiced); 1 tbsp olive oil; 1 egg (beaten); sea salt and black pepper (to taste)