Clean the savoy cabbage and peppers and cut into strips. Heat the oil in a coated pan and fry both for 5-10 minutes. Season with tarragon and deglaze with the stock. Melt the processed cheese in it and season the sauce with salt, pepper, mustard, paprika powder and nutmeg.
Place the tortellini in a baking dish, spread the vegetable sauce on top and bake the gratin in the preheated oven at 220 ° C (gas level 3, fan oven 180 ° C) on the middle rack for about 20 minutes.