Make Ahead Sweet – Sour Meatballs

4 slices white sandwich bread, torn into pieces
1/2 c. whole milk
2 large egg yolks
1/2 lb. ground pork
2 garlic cloves, minced
1/2 c. finely chopped fresh parsley
1 tsp. salt
2 tsp. pepper
2 1/2 lbs. 85% lean ground beef

1 Tbsp. vegetable oil
1 onion, minced
1 (28 oz.) can tomato sauce
2 Tbsp. Dijon mustard
2 1/2 c. apricot preserves
1/4 c. packed dark brown sugar
3 Tbsp. Worcestershire sauce
1/4 tsp. red pepper flakes

Adjust oven racks to upper-middle and lower-middle positions. Heat oven to 450°. Using fork, mash bread, milk and egg yolks in large bowl until smooth. Add pork, parsley, garlic, salt and pepper and mix until incorporated. Add beef and knead gently until combined. Form mixture into 1 1/4-inch meatballs (use 1 1/4-inch melon baller or one Tbsp. measuring spoon); should have about 80. Bake meatballs on two rimmed baking sheets until cooked through and beginning to brown, 12-15 minutes, switching and rotating sheets halfway through cooking. Let cool to room temperature, then refrigerate until firm, about 30 minutes. Transfer to large zipper-lock bag and freeze for up to one month. To make sauce, heat oil in Dutch oven over medium-high heat until shimmering. Cook onion until softened, about five minutes. Whisk in tomato sauce, preserves, sugar, Worcestershire, mustard and pepper flakes and bring to boil. Reduce heat to medium-low and simmer until sauce is thickened, about 15 minutes. Let cool to room temperature. Transfer to airtight container and freeze for up to one month. To serve, reheat sauce, covered and stirring occasionally, in Dutch oven over medium-low heat. Once sauce reaches simmer, stir in frozen meatballs and cook until heated through, 10-15 minutes. Serves 20.