Place the tomatoes, chillies plus 1 tsp of their sauce, garlic, cumin, oregano and salt in a blender.
Add the chicken stock and process until quite smooth.
Place the beef, pork, cumin, garlic, 1 tsp salt and a grind of pepper in a bowl. Mix well
Stir in the breadcrumbs, eggs and milk.
To check the seasoning, cook a small amount of mixture and taste it.
Form the mince mixture into small balls about the diameter of a 20-cent piece.
Heat a large frying pan over a medium heat with a splash of olive oil. Add the meatballs and brown gently for 2 minutes.
Add the sauce and cook gently for about 6 minutes, stirring occasionally, until the sauce starts to thicken.
Reduce the heat to medium-low and cook, uncovered, until the sauce has reduced to about half its original volume and coats the meatballs.
Spoon the meatballs onto a serving plate, and grate a little manchego or pecorino over the top