Prepare the filling. Fry the onion with mushrooms and carrots in a frying pan in oil for 10-13 minutes until the vegetables are soft. Add salt and pepper. Place the fried vegetables and mushrooms in a separate plate and cool. Add dill and garlic. Stir.
Prepare the meat. First make a small cut on the wide side of the fillet. Then carefully make a deep cut inside the fillet with a knife, but not all the way through. You should get pocket-like pieces. Rub the prepared fillet with salt, pepper, paprika, and pour in 0.5 tbsp. of oil.
Stuff the fillet. Place the prepared mushroom filling in the pockets of the fillet. Place the stuffed breast on pieces of baking paper folded into boats. Bake the dish on a baking sheet at 200℃ for 30-40 minutes. Remove the baking sheet from the oven, sprinkle the fillet with cheese and bake for another 5 minutes until the cheese melts.