Soak the panko breadcrumbs in whole milk for about 5 minutes until they soften. In a mixing bowl, combine with an egg, grated garlic, kosher salt, black pepper, nutmeg, and allspice. Add the lean ground beef and ground pork, mixing until just combined. Shape into small meatballs.

In a large skillet, melt 1 tablespoon of salted butter over medium heat. Add the frozen pierogies and a splash of water—cover to steam for about 5 minutes. Remove the lid and pan-fry in remaining butter for 3-4 minutes until golden brown.

In the same skillet, add 2 tablespoons of olive oil and heat. Carefully place meatballs ensuring not to overcrowd. Cook for about 7-9 minutes, turning occasionally until golden and cooked through, using a meat thermometer to check 160°F.

Reduce heat to medium and melt remaining butter. Add chopped onion, sautéing until translucent and golden for about 3-5 minutes. Sprinkle flour, stirring for 1 minute, then gradually whisk in broth and milk. Let simmer for 5 minutes to thicken.

Once sauce has thickened, carefully add cooked meatballs and golden pierogies back into the skillet. Stir gently to coat, cooking for an additional 2-3 minutes until everything is warmed through.

Remove from heat and sprinkle with freshly chopped parsley or dill. Serve directly from the pan or plate up.