Melt the butter in a skillet over medium-low heat. Meanwhile, finely dice the onion. Once the butter has melted, add the diced onion to the pan and saute until the onions are soft and slightly browned (~5 minutes).
Place the sauted onions in a medium sized mixing bowl. Place the skillet back onto the burner and turn off the heat.
Add the remaining meat ingredients to the bowl with the onion. Mix the ingredients until thoroughly combined (hands will make the best spoon here).
Then, form the meat into individual meatballs measuring about 1-2 inches in diameter.
Turn the heat to medium and place the meatballs on the pan. Cover the pan with a lid and allow the meatballs to cook, uncovered, until the outsides are no longer pink (ideally, the meatballs are still pink on the inside).
Then, turn the heat up to high. Turn the meatballs and allow them to cook until all sides are browned. Note: The pan should be uncovered at this point. Additionally, the meatballs should be turned frequently to ensure that all sides are browning and that none are burning. While the meatballs are cooking, mix together all of the sauce ingredients in a mixing bowl. Use a fork or whisk to help break up the flour and sour cream.
Once all sides of the meatballs are browned, pour the sauce mixture over the meatballs. Allow the sauce to cook over high heat until the sauce is slightly thickened (5-10 minutes).
Remove the pan from the stove and allow to slightly cool before serving. Then, enjoy!