The Scandinavian countries are known for flavoring their foods with nutmeg and other spices most Americans would only consider for baking. Try Swedish meatballs for a change of taste!
Heat oven to 250F and set an oven-proof casserole dish to one side.
Cut the onion in half lengthwise, so each half still has a small part of the root at the end. Peel the halves. Place a box grater on top of a plate and grate the onion. If you typically “cry” while prepping onions, try refrigerating your onions for 24 hours before using.
In a medium skillet over medium heat, put a tablespoon of butter and allow to melt. Then put in the grated onion, any onion juice that the plate captured, and a pinch of salt. Allow to cook until the grated onion is soft, about 10 minutes. You are not attempting to brown or carmelize the onion at all, just get it cooked through.
To prep the meat mixture, you can use a stand mixer with a paddle attachment. If you do not have a stand mixer, you can just use your clean hands. Put in the bowl for the mixer the ground beef, the egg yolks, 1 tsp each of kosher salt and black pepper, the almond meal, the allspice, and nutmeg. Mix until all ingredients are thoroughly incorporated.
Put one tablespoon of butter into a large skillet and bring to medium-high heat. Using a scoop or your fingers, scoop out 1 oz. of the meat mixture and roll between your palms to create a meatball. (You can also make the meatballs in a 1/2 oz. size for a cocktail-sized meatball.) As you form meatballs, put them in the skillet and brown on all sides. As the meatballs become brown, transfer them from the skillet to the oven-proof casserole and keep them warm in the oven.
After the meatballs are browned and put in the oven, take another clean large skillet and put it over medium heat. Put 1 tbsp. of butter and allow to melt then stir in the potato starch. Allow to cook until the potato starch looks thoroughly incorporated. Pour in the beef broth and stir until the butter/starch mixture is thoroughly incorporated and is starting to thicken. Pour in the heavy cream. Add salt and pepper to taste and a 1/2 tsp. of nutmeg. Turn the heat up to medium-high, stirring constantly until the sauce is thickened and smooth.
Spoon sauce over meatballs and enjoy!