Finely chop the garlic and onion and sauté in 1 teaspoon olive oil. Add the spinach and season well with salt, pepper and nutmeg.
Slice the chicken breast fillets, pound them flat, season with salt, pepper and brush with 1 teaspoon of mustard. Dice the mozzarella and spread over the meat with the spinach. Roll up and secure with wooden sticks. Fry the stuffed chicken breast on baking foil all around fat-free and cook in the preheated oven on the middle rack at 180 ° degrees (gas: level 2) on baking foil for about 10 minutes.
For the sauce, finely chop the onion and fry half in 1 teaspoon olive oil. Pour in the broth and bring to the boil. Stir in cheese and parsley and season with salt, pepper, sugar and nutmeg.
For the salad, cut the tomatoes into slices, mix with the remaining diced onion and basil leaves. Mix the rest of the olive oil with the orange juice, tomato juice, balsamic vinegar and the rest of the mustard. Season with salt and pepper and pour over the salad.
Serve the stuffed chicken breast with sauce and salad.