1. Rinse and soak the rice in cold water for about 30 minutes, then drain.
2. In a large pot, bring water to a boil, add the rice, and a pinch of salt. Parboil for about 5-7 minutes.
3. Stir in the pumpkin puree and saffron threads into the boiling rice, then drain the rice thoroughly.
4. In a bowl, mix the yogurt, sour cream, lemon juice, vegetable oil, and beaten eggs. Add salt and pepper to taste.
5. For the beef stuffing, season the beef with allspice, cinnamon, cloves, and ginger. Brown in a pan until cooked through, and mix in caramelized onions and mint.
6. In a non-stick pot, layer a portion of the rice mixture, followed by the beef stuffing, and top with the remaining rice mixture to form layers.
7. Cover the pot with a tight-fitting lid to prevent steam escape and cook on high heat for 10 minutes to build steam, then reduce to low heat for 60 minutes.
8. Once cooked, allow to cool slightly, then invert onto a serving dish. The result should be a beautiful rice cake with a crispy, golden crust.