Bring 2 large pots of salted water to a boil over medium-high heat. Add potatoes to one pot; cook for 20 minutes. In the other pot, cook cleaned, washed, and cut beans for 15 minutes. While both cook, peel and chop onion and garlic; clean tomatoes and cut into cubes.
Heat oil in a large pan over medium-high heat. Add minced meat, chopped onion, and minced garlic. Fry for 5 minutes until meat is cooked through. Season with salt and pepper to taste.
Drain beans. Drain potatoes, rinse with cold water, peel, and cut into thick slices.
Transfer cooked meat to a baking dish. Mix potatoes, beans, and tomatoes together. Spread mixture over meat. Roughly grate sheep cheese; mix with whipped cream. Season cheese-cream mixture with salt and pepper to taste. Spread evenly over casserole.
Preheat oven to 200°C (400°F). Bake casserole for 15 minutes until top is golden brown and heated through.