Preheat the oven to 400°.
Combine the ground meat, onion, garlic, eggs, Parmesan, dill, garlic powder, onion powder, spinach and salt.
Roll into balls and place on lined baking sheet.
Bake for 15-20 minutes (depending on size of meatballs - internal temp should reach 160°). Remove from oven and set aside.
In a pan, simmer the chicken stock to a boil on medium-high heat.
Make a slurry with the cornstarch and water and add it to the pan, stirring constantly.
Once the mixture begins to thicken, add the butter.
Once the butter melts, add the Greek yogurt and stir.
Season the sauce WELL with salt and dill. Roughly 2 tsp salt and 1 tsp dill should do the trick.
Settle the cooked meatballs into the sauce and stir to coat.
Serve over rice or egg noodles.