- Combine onion, bread crumbs, 1/4 teaspoon salt, pepper, nutmeg and cardamom (if using) in a large bowl. Add turkey and pork; gently mix to combine (do not overmix). Using a scant 2 tablespoons for each, make about 20 meatballs.
- Heat oil in a large nonstick skillet over medium heat. Add the meatballs and cook, turning occasionally and reducing the heat if the pan gets too hot, until almost cooked through, 10 to 12 minutes. Transfer to a plate.
- Add mushrooms to the pan and increase heat to medium-high. Cook, stirring occasionally, until their liquid has been released and evaporated, 8 to 10 minutes.
- Whisk broth and flour in a bowl and add to the pan along with the meatballs. Bring to a simmer and cook until the meatballs are just cooked through and the sauce is thickened, about 2 minutes. Remove from the heat. Add sour cream, parsley, jam and the remaining 1/2 teaspoon salt to the sauce; gently stir until combined.
Tip: To make your own fresh breadcrumbs, trim crusts from whole-wheat bread. Tear bread into pieces and process in a food processor until coarse crumbs form. To make fine breadcrumbs, process until very fine. To make dry breadcrumbs, spread coarse or fine breadcrumbs on a baking sheet and bake at 250°F until dry, about 10 to 15 minutes. One slice of bread makes about 1/2 cup fresh breadcrumbs or about 1/3 cup dry breadcrumbs. For store-bought coarse dry breadcrumbs we like Ian’s brand, labeled “Panko breadcrumbs.” Find them at well-stocked supermarkets.
To Make Ahead: Freeze cooked meatballs in sauce airtight for up to 3 months. Defrost before reheating.