Preheat oven to 400°. Lightly grease a baking sheet with some oil or cover it with parchment paper.
Combine the ground beef, ground pork, egg, minced onion, pressed garlic, herbs, salt, and pepper in large mixing bowl. Squeeze milk out of the slice of bread, break it up, and add crumbled bread to the bowl. (Discard squeezed milk.)
Mix everything very well.
Grease your hands with some cooking spray. To get even meatballs, use a cookie scoop. I use #40 scoop but you can use a slightly larger one. Try to keep the meatballs about 1 inch in diameter. (You can make meatballs a little bigger or smaller according to your own preference. Just remember to adjust cooking time if making bigger or smaller meatballs.)
Quickly roll all the meatballs and add them to the baking sheet, close together but not touching.
Bake the meatballs for 18-22 minutes, depending on the size.
Whisk all the ingredients for the sauce together and preheat a 12-inch skillet over medium heat.
Pour the sauce into the pan and simmer for about 6-8 minutes. Make sure to slowly stir every couple of minutes while it's simmering.
Add meatballs (just meatballs, but the juices left from baking meatballs) to the sauce. Carefully stir meatballs and sauce until coated and let them cook for just a few minutes.
Transfer the meatballs and the sauce onto a serving bowl and serve.
Keeping them warm in a crock pot:
You can also serve these meatballs in a crock pot to keep them warm for the party.
Prepare the meatballs and the sauce per instructions above but combine them together in a crock pot instead of the skillet.
Set the Crock pot to "warm" setting, cover, and let them stay in there for the party. You will want to stir them from time to time.