Cut out twelve 2-inch rounds from puff pastry sheet; place on a baking sheet. Bake at 400 degrees until golden, about 12 minutes. Combine ground beef, cilantro, garlic, salt and pepper; form into twelve 1-inch balls. Press an avocado cube into each and shape into patties; fry until cooked through, about 5 minutes. Split the pastry "buns" and assemble the sliders with the patties and desired condiments.