Heat oven to 425°F. Line a rimmed sheet pan with foil and lightly oil it.
Soak breadcrumbs in milk for 5 minutes in a large bowl.
Add beef, mayonnaise, onion, garlic, salt, pepper, and pumpkin pie spice. Mix gently until just combined.
Form 1½-inch meatballs and arrange on the prepared pan. Drizzle with a little olive oil.
Bake 12–15 minutes, until browned and cooked through to 160°F.
Simmer pumpkin puree, cider, brown sugar, maple syrup, soy sauce, Dijon, pumpkin pie spice, cinnamon, salt, and red pepper flakes in a saucepan over medium heat.
Stir cornstarch with water, then whisk into the saucepan. Cook 1–2 minutes until thick and glossy. Finish with butter.
Toss baked meatballs in the hot glaze and simmer 2–3 minutes to coat well.
Sprinkle with parsley and serve warm as appetizers or over rice.
Notes
Variation: Swap ground turkey for beef and add a splash more cider to keep the glaze silky. For a party, hold meatballs warm in a slow cooker on Low for up to 2 hours. Leftovers keep 3–4 days refrigerated; reheat gently and thin the glaze with a spoonful of cider if needed.This recipe is an original creation inspired by classic Pumpkin Pie Glazed Meatballs flavors. All ingredient ratios and instructions are independently developed.