With a sharp knife, make deep cuts on the down side of each drumstick next to the bone to allow the heat of the grill to reach the centre of the meat. Add Vegeta marinade to the drumsticks and leave them for 30 minutes to aromatize the meat.
Place on the hot grill and cook for 10 to 12 minutes on each side, turning the drumsticks from time to time.
To make the sauce, mince the onion and sauté with a little melted butter on low heat for about 10 minutes. Stir in the flour, mix well and carefully add milk stirring with a balloon whisk.
When the sauce boils, add mustard and Vegeta Universal, season with salt and pepper to taste and cook on low heat until the sauce thickens.
Before grilling chicken or other poultry, it is very important to make deep cuts in the meat to allow the heat to penetrate and cook the meat around the bone.