Add 1 tbsp olive oil to a large pot or dutch oven, cook the diced onions & garlic 3-5 minutes.
In a large bowl, combine the cooked onions and garlic, ground beef, ground pork, breadcrumbs, eggs, 1 tsp salt, 1 tsp black pepper, paprika and oregano.
Use your hands to roll the mixture into approximately 24 golf ball sized meatballs.
In the same pot you cooked the diced onions, add an additional tablespoon of olive oil, bring to medium-high heat and place the meatballs in the pot, brown on all sides, 3-5 minutes.
Remove the meatballs from the pot and set aside.
Keep the pot over medium-high heat.
Add flour to the pot with the drippings from the meatballs.
Scrape up all of the meatball drippings and combine with the flour.
Stir in the beef broth and bring to a boil.
Add the remaining ½ tsp kosher salt and ½ tsp black pepper.
Add the capers, lemon juice, lemon zest and bay leaf.
Stir to combine, then add the meatballs back into the pot with the potatoes.
Cover, reduce heat to medium low and simmer for 45 minutes, or until potatoes are fork tender. Before serving, add the sour cream to the pot and stir into the sauce.
Optionally top with fresh chopped parsley when serving.