In a bowl, combine the beef with salt, pepper, and minced garlic. Mix thoroughly and refrigerate for at least 15 minutes.
Halve the onion and cut out large rings. Cut the cheddar cheese into square slices.
Fill each onion ring with a small amount of seasoned beef. Top with a cheddar slice. Add another small amount of seasoned beef on top and press firmly.
Place flour in one bowl, breadcrumbs in a second bowl, and whisk the eggs in a third bowl.
Working with one ring at a time, dip in egg, then flour, then breadcrumbs. For extra crispness, dip again in egg and breadcrumbs.
Heat oil for deep-frying to 175°C (350°F). Fry the onion rings, a few at a time, for 2–3 minutes until golden brown. Drain on paper towels and serve with your favorite sauces.