Combine the meatball ingredients (except the butter) in a medium bowl and mix well.
Form into 12 meatballs.
Heat the 2 Tbsp of butter in a large, nonstick saute pan.
Cook the meatballs on medium heat in the butter until browned on all sides and cooked through (2-3 minutes per side.)
Remove the meatballs from the pan and set aside.
Add the 1 Tbsp of butter and the 2 cups of sliced mushrooms to the pan.
Cook until the mushrooms are golden and fragrant (4-5 minutes.)
Remove the mushrooms from the pan.
Add the onions and garlic and cook for 3-4 minutes or until softened and translucent.
Remove the onions from the pan.
Add the beef broth to your pan and scrape the bottom to get all the yummy bits off.
Whisk in your sour cream and xanthan gum until smooth.
Add the meatballs, mushrooms, onions and garlic back to the pan and stir.
Season with salt and pepper to taste.
Simmer on low for 20 minutes.
Garnish with the fresh parsley right before serving.
The Binding Mechanics of Almond Flour
Almond flour replaces standard wheat breadcrumbs, introducing high fat and protein content without the gluten network. Mix the ground beef, egg, almond flour, and seasonings gently; overworking the protein strands will yield a dense, rubbery meatball rather than a tender one. Brown these formations in a wide sauté pan over medium heat for two to three minutes per side to achieve Maillard browning, which develops foundational savory depth.
Thickening Without Flour via Xanthan Gum
Xanthan gum acts as a powerful polysaccharide thickener that alters liquid viscosity at extremely low concentrations. Whisk this powder thoroughly alongside sour cream into the simmering beef broth to prevent clumping. Maintain a low simmer for 20 minutes so the proteins in the dairy hydrate evenly without splitting or curdling from excess heat.
Aromatics and Pan Fond Extraction
Deglazing the pan with broth after cooking the mushrooms and onions dissolves the caramelized fond stuck to the bottom. Scrape these browned bits into the liquid using a flat wooden utensil to incorporate concentrated umami compounds directly into the sauce. Mushrooms release their internal moisture during the initial four to five-minute high-heat sauté, concentrating their natural glutamates before returning to the pan.