Step 1

For the Meatballs: Whisk egg and cream together in medium bowl. Stir in bread and set aside. Meanwhile, in stand mixer fitted with paddle attachment, beat pork, onion, nutmeg, allspice, pepper, brown sugar, salt, and baking powder on high speed until smooth and pale, about 2 minutes, scraping bowl as necessary. Using fork, mash bread mixture until no large dry bread chunks remain; add mixture to mixer bowl and beat on high speed until smooth and homogeneous, about 1 minute, scraping bowl as necessary. Add beef and mix on medium-low speed until just incorporated, about 30 seconds, scraping bowl as necessary. Using moistened hands, form generous tablespoon of meat mixture into 1-inch round meatball; repeat with remaining mixture to form 25 to 30 meatballs.

Step 2

Heat oil in 10-inch straight-sided sauté pan over medium-high heat until edge of meatball dipped in oil sizzles (oil should register 350 degrees on instant-read thermometer), 3 to 5 minutes. Add meatballs in single layer and fry, flipping once halfway through cooking, until lightly browned all over and cooked through, 7 to 10 minutes. (Adjust heat as needed to keep oil sizzling but not smoking.) Using slotted spoon, transfer browned meatballs to paper towel-lined plate.

Step 3

For the Sauce: Pour off and discard oil in pan, leaving any fond (browned bits) behind. Return pan to medium-high heat and add butter. When foaming subsides, add flour and cook, whisking constantly, until flour is light brown, about 30 seconds. Slowly whisk in broth, scraping pan bottom to loosen browned bits. Add brown sugar and bring to simmer. Reduce heat to medium and cook until sauce is reduced to about 1 cup, about 5 minutes. Stir in cream and return to simmer.

Step 4

Add meatballs to sauce and simmer, turning occasionally, until heated through, about 5 minutes. Stir in lemon juice, season with salt and pepper, and serve.