In a large bowl, combine the ground beef, ground pork, onions, eggs, salt, pepper and spices. Mix thoroughly by hand or with a stand mixer.
Shape meatballs into 1 or 1.5 inch rounds and set them on parchment paper.
Heat the butter in a saute pan over medium-low heat.
Add meatballs to the saute pan, a few at a time (do not overcrowd). Saute until the meatballs are browned on all sides. Remove the meatballs and put them in a crock pot (or in an oven proof dish in warmed oven at about 200 degrees F). Continue until all of the meatballs are cooked.
Drop the heat under the skillet to low and add the flour. Whisk the flour until it is lightly browned, about a minute or two.
Gradually add the beef stock. Whisk until the flour is dissolved and the mixture starts to thicken.
Add the cream and simmer until the sauce is gravy-thick. Then cover the meatballs in the crock pot (or the oven proof dish) with the gravy and serve.