Kroppkakor (Swedish Potato Dumplings Stuffed with Bacon and Onion)

Ingredients

• 3 lb. russet potatoes, peeled and cut into 1" pieces
• 2 ¹⁄₂ cups flour, plus more for dusting
• 2 eggs, plus 1 yolk
• Kosher salt, to taste
• 1 tbsp. olive oil
• 1 lb. sliced bacon, roughly chopped
• 1 large yellow onion, minced
• 1 tbsp. ground allspice
• Lingonberry preserves and sour cream, for serving