To make the sauce,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.
To make the meatballs,place the beef,pork,cumin,garlic,1 tsp salt and a grind of pepper in a bowl.
Mix well,then 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.
To serve,spoon the meatballs onto a serving plate,and grate a little manchego or pecorino over the top.
Correction:The quanitity of the chipotle chillies in adobo sauce has been clarified from the original version of this piece.