Combine chicken, onion, egg, breadcrumbs, garlic, allspice, and nutmeg in a bowl. Season with salt and pepper. Form mixture into 10 meatballs.
Heat oil in a large nonstick skillet over medium heat. Add meatballs and cook, turning occasionally, until golden brown on all sides and cooked through, 12 to 14 minutes. Remove to a plate. Add flour to pan and cook, stirring 30 seconds. Slowly add broth and cream and cook, stirring occasionally, until thickened, 2 to 3 minutes. Add meatball and any juices and cook, turning, until coated, about 1 minute. Garnish with parsley and serve over mashed potatoes with lingonberry jam alongside.
