Preheat oven to 400 degrees Fahrenheit and line a baking sheet with parchment paper.

In a large bowl, whisk together grated onion, half-and-half, cornstarch, egg, kosher salt, ground nutmeg, ground allspice, and ground black pepper until well combined.

Add meatloaf mix (or ground beef, pork, and veal) to the bowl and gently blend to incorporate the ingredients.

Scoop the meat mixture into thirty 1 1/2-inch meatballs and place them on the prepared baking sheet.

In a nonstick skillet, heat unsalted butter and olive oil over medium heat.

Roll the meatballs between your palms to ensure a round shape.

Brown the meatballs in batches in the butter mixture, approximately 2 minutes per side. Do not cook through.

Carefully transfer the browned meatballs to a Dutch oven.

Pour off any excess fat from the skillet and return it to the burner over medium heat.

Prepare the brown gravy by deglazing the skillet with 3 1/2 cups of beef broth, scraping up any browned bits from the bottom of the pan.

Stir in beef base and bring the mixture to a boil over medium heat.

In a separate cup, whisk together all-purpose flour and Kitchen Bouquet with the remaining 1/2 cup of beef broth until smooth.

Add the flour mixture to the simmering broth, stirring constantly to avoid lumps.

Cook the gravy for 5 minutes, skimming off any foam if necessary, and season with salt and pepper to taste.

Pour the prepared gravy over the meatballs in the Dutch oven.

Cover the pot and braise in the preheated oven for 35-40 minutes, or until the meatballs are cooked through.

Serve the Norwegian meatballs in brown gravy over mashed potatoes or buttered noodles.