Add lentils to a large pot with 600ml of vegetable stock. Bring to a boil, then reduce heat and simmer for 15-20 minutes until lentils are just tender but still hold their shape. Drain any excess liquid and set aside.

While lentils cook, heat olive oil in a large deep skillet over medium-high heat. Add sliced onions and cook, stirring occasionally, for 25-30 minutes until deeply golden and caramelized. Reduce heat if onions brown too quickly.

Remove two-thirds of the caramelized onions and set aside for topping. Keep the remaining onions in the skillet.

Add cumin, coriander, allspice, and cinnamon to the skillet with the onions. Stir for 30 seconds until fragrant.

Add the rinsed rice and cooked lentils to the skillet. Stir to combine with the spiced onions.

Pour in the remaining 400ml vegetable stock, add salt and pepper, and bring to a boil. Reduce heat to low, cover tightly, and simmer for 18-20 minutes until rice is tender and liquid is absorbed.

Remove from heat and let rest covered for 5 minutes. Fluff gently with a fork.

Transfer mujaddara to a serving platter, top generously with reserved crispy caramelized onions, garnish with fresh parsley, and serve with lemon wedges.