Melt the butter and sweat the flour in it. Deglaze with the chicken stock while stirring, stir in the cream. Let simmer for 10 minutes. Add the herbs to the sauce and season with salt, pepper, sugar and lemon juice.
Season the chicken breast fillets and place in a baking dish, distribute the herb sauce on the fillets and sprinkle with the parmesan. Place the mold in the preheated oven (fan oven 200 degrees) for 30 minutes.