Heat coconut oil in a frying pan, add shallot and fry for 2 minutes, add minced beef, cook for 3-4 minutes, stir in salsa, chili flakes, garlic powder, salt and pepper. Cook on low for 10-12 minutes.
Preheat the oven to 400 F. Line a baking tray with parchment paper. Mix cheddar cheese and mozzarella in a bowl and divide this mixture into 4 parts. Place shells on the baking tray and bake for 5-7 minutes.
Let cool for a minute, add 2 tbsp of beef mixture on each shell and roll quickly. Serve immediately, topped with sour cream (optional).