Season the fillets with salt and pepper. Place a frying pan on the heat and add the olive oil. When it's hot, add the fillets and sauté for a bit on both sides. Add 1 tablespoon of butter and the thyme. Let the fillets become golden-brown and remove them from the pan. Place them in a plate and cover to keep them warm. In the same pan, add the onion and sauté for 1 minute. Add the mushrooms and the garlic and sauté on high heat for 2-3 minutes. Remove them from the pan and keep them warm. In the same pan add the remaining butter (1 tbsp) and stir until it melts. Add the chicken stock, Balsamic cream, fresh cream and the grated halloumi. Stir and bring the fillets and mushrooms back into the pan. Reduce the heat and cook for 2-3 minutes. Turn the fillets over and continue cooking until the sauce is combined.
Garnish with parsley and serve.