In a large mixing bowl, combine the ground beef, breadcrumbs, onion powder, parsley, allspice, nutmeg, garlic powder, egg, Worcestershire sauce, salt, and black pepper. Mix until just combined, then form into 12 equal-sized meatballs.
In a large pan over medium heat, add a drizzle of olive oil. Sear the meatballs on all sides until browned, about 1-2 minutes per side. Remove the meatballs from the pan and set aside.
In the same pan, add the butter and melt over medium-low heat. Add the shallots with a pinch of salt, and sauté until translucent, about 2 minutes. Add the minced garlic and fresh thyme, and sauté for another 1 minute until fragrant.
Next add the Dijon mustard, and Worcestershire sauce. Stir into the shallots and garlic.
Sprinkle the flour over the shallot mixture and stir constantly for about 2 minutes to cook out the raw flour taste. Slowly add the beef broth, stirring continuously to combine.
Add the meatballs back into the pan, cover, and cook on low for 10-15 minutes, or until the meatballs are cooked through.
Stir in the sour cream and chopped chives, and season with salt and black pepper to taste.
Serve these delicious Swedish meatballs over mashed potatoes, rice, or egg noodles.
