Heat some oil in a skillet and once hot add the meatballs, browning on all sides. Transfer the meatballs to a plate and discard all but a tablespoon or so of grease.

Add the onions to the skillet and fry until translucent and golden brown. Add the garlic and fry for another minute (don't fry garlic too long or it becomes bitter). Add the mushrooms and fry until they've released their juices and they're mostly evaporated. Transfer the mushroom mixture to a bowl and set aside.

Add the butter to the skillet and melt it. Add the flour and whisk until dissolved. Continue whisking vigorously for another minute or two until the flour mixture is a deep golden brown. (We're creating what's called a roux, a French term and the grand secret for creating an irresistibly rich and flavorful sauce.)

Pour in the hot broth while continually whisking to prevent clumping. Continue to whisk while bringing the mixture to a simmer. Add the cream and whisk until combined. Continue to simmer for another minute or so until the sauce is thickened. Return the mushroom mixture to the sauce and add the pepper, salt and paprika. Stir in the sour cream and dill.

Return the meatballs to the sauce, stirring to coat them, and simmer covered for about 10 minutes, stirring occasionally.