Set the cottage cheese and milk for the sauce out on the counter first so they lose their chill. Room-temperature dairy is less likely to separate. Heat the oven to 425°F and line a sheet pan with parchment.
In a large bowl, stir the panko into the 2 tbsp of milk and let it soak for 5 minutes. This helps keep the meatballs juicy.
Add the beef, egg, Parmesan, garlic, Italian seasoning, onion powder, Worcestershire sauce, red pepper flakes, salt, and pepper. Mix with your hands only until combined, since overmixing makes them tough.
Using a 1 tbsp cookie scoop, portion out 35 mini meatballs onto the pan, then quickly roll each one with wet hands. Crowding is fine because they shrink as they cook. You could even go small if you want just bake for less time.
Bake at 425°F for 10 minutes, then broil 1–2 minutes until browned on top. Pull them at 160°F.
While the meatballs bake, put a pot of salted water on to boil. Cook the spaghetti according to the package instructions.
Blend the cottage cheese, milk, Parmesan, garlic powder, arrowroot, salt, and pepper on high for 60–90 seconds, until completely smooth.
As the pasta cooks, pour the sauce into a large skillet over medium-low. Warm it for 5–7 minutes, whisking often, until it thickens. Keep the heat low so it doesn't burn.
After draining, give the pasta 1 minute to cool slightly so it's close to the sauce's temperature. With the heat on low, add it to the skillet and toss with tongs until every strand is coated. It will thicken as it sets. If the sauce gets too thick, add a splash of water.
Turn off the heat. Fold in the meatballs. Finish with parsley and more Parmesan, pepper or red pepper flakes as desired. Serving size: 7 meatballs and 307 grams of pasta.
Notes
Serving size: 7 meatballs and 307 grams of pasta.
Leftovers: add a splash of milk or broth to loosen the sauce when reheating.
Keep the dairy at room temperature and the heat low so the sauce stays smooth.
You can definitely make these meatballs even smaller if desired. Just bake them for less time until cooked through.
Nutritional information is an estimate and will vary with substitutions.