How to cook
Preheat the oven to 356°F (180 degrees).
Prepare a baking sheet with a layer of parchment paper.
Mix the breadcrumbs, fresh milk, egg, black pepper, salt, ground allspice and nutmeg and the finely chopped parsley. Mix the ingredients well until they form a paste. Set aside.
In a deep pan heat the olive oil and butter to a moderate temperature, saute the finely chopped onion, stir for 3-4 minutes until it softens and add the crushed garlic. Add the sauted onion to the breadcrumbs, as well as, the two kinds of minced meat.
Mix well to incorporate all the ingredients, if it is too dry you can add 2-3 tbsp of milk, but not to become too moist. Use an icecream scoop spoon around 1.2″ (3 cm) in diameter, to form small meatballs. Arrange the meatballs on the baking sheet covered with parchment paper.
Bake for no more than 20 minutes in a preheated oven at 356°F (180 degrees). The meatballs will finish cooking with the sauce. Remove the baking sheet from the oven and set aside.
For the sauce
In a deep pan heat the olive oil and butter to a moderate temperature. Add the flour stirring constantly with a wooden spoon, until the flour changes it's color. Pour gradually the chicken and beef stock, whisking contstantly to prevent it from lumping.
Add the cream, soy sauce, mustard, Worcester sauce, lemon juice, sugar, white pepper and a pinch of salt if you wish. After adding each ingredient stir with a wooden spoon.
Simmer for 10-15 min stirring occasionally. Then add the meatballs and simmer for 10 more minutes. Remove from the stove and sprinkle with finely chopped parsley.