Sprinkle crumbs from 2 pouches of granola bars evenly into bottoms of muffin cups. Drizzle 2 tablespoons of the chocolate syrup onto granola crumbs (about 1/2 teaspoon each). Spoon 1/3 cup frozen yogurt onto crumb mixture; smooth with back of spoon. Drizzle with remaining 2 tablespoons chocolate syrup. Top with remaining 2 pouches of granola crumbs. Press crumbs gently into top with fingers.