Place a sprig of rosemary on the top of the arista by placing it in the string and lay the meat in a saucepan together with the extra virgin olive oil and the peeled garlic clove. Brown for a few minutes on all sides, blend with the white wine and season with salt and pepper.
Clean the celery, carrots and onions and cut everything into chunks. Transfer the meat along with the smells onto a baking sheet and season with the cooking juices, milk and bay leaves. Bake in the oven at 160 ° C for 1 hour, raise the temperature to 180 ° C and continue for another hour. When cooked, place the arista on a cutting board and let it cool.
Prepare the sauce by blending the dressing together with the mustard until you get a smooth cream without lumps. Season with salt. Cut the loin into very thin slices, complete with the mustard sauce and serve.
