• Place bread cubes in a large mixing bowl; pour milk over bread cubes and let sit for about 6 to 8 minutes, or until the bread has absorbed all the milk.
• Using two forks, shred the bread into tiny pieces.
• To the bread mixture add grated onions, egg, garlic, beef, pork, salt, pepper, allspice, and nutmeg.
• Mix everything together until well combined. It’s best to use your hands to mix it all together.
• At this point, you can chill the mixture for 15 to 30 minutes so it’s easier to roll out the meatballs. This is not a must, but it does help.
• Form the mixture into about 24 meatballs. Mixture will be wet.
• Set a large frying pan over medium-high heat; heat 1 tablespoon butter and 1 tablespoon olive oil.
• Working in batches, brown the meatballs on all sides; this should take about 5 to 6 minutes for each batch, depending on the size of the meatballs. Use a spoon to turn them over; turn over gently so they don’t break apart.
• Transfer cooked meatballs to a plate and cover with foil.

Make the sauce:

• Add 3 tablespoons butter to the pan and melt over medium heat.
• Whisk in the flour; continue to whisk until dissolved and brown, about 2 minutes.
• Slowly pour in the broth and whisk; the broth will sputter and seize up a bit, but just keep stirring and the sauce will eventually loosen up.
• Add the cream while continuously whisking. Don't stop whisking because the heavy cream will curdle.
• Whisk in Dijon mustard, salt, and pepper; bring mixture to a simmer and continue to cook until thickened and smooth.
• Stir to combine the flavors.
• Return meatballs to the pan; cook on low heat just to warm through and gravy to thicken, about 6 to 8 minutes.
• Remove from heat and serve over mashed potatoes or noodles.
• Or, add toothpicks to each meatball and serve as an appetizer.