Creating Lamb Vindaloo is a process that involves marinating the meat and slowly cooking it to perfection. Follow these steps to achieve a mouth-watering result:

Step 1: Marinate the Lamb

1. Prepare the Marinade: In a large bowl, combine the minced garlic, grated ginger, white vinegar, cumin seeds, coriander powder, turmeric powder, red chili powder, garam masala, mustard seeds, fenugreek seeds, and salt.
2. Marinate the Lamb: Add the lamb pieces to the marinade, ensuring they are well-coated. Cover the bowl with plastic wrap and refrigerate for at least 4 hours or overnight for best results.

Step 2: Cook the Lamb Vindaloo

1. Sauté the Spices: Heat vegetable oil in a large, heavy-bottomed pan over medium heat. Add the mustard seeds, black peppercorns, cloves, cinnamon stick, and bay leaves. Sauté for about 2 minutes until the spices are fragrant.
2. Cook the Onions: Add the finely chopped onions to the pan. Cook until they turn golden brown. This should take about 10 minutes.
3. Add Tomatoes and Lamb: Stir in the pureed tomatoes, followed by the marinated lamb. Cook for 5-7 minutes, stirring occasionally until the lamb is browned on all sides.
4. Simmer: Pour in the water or broth. Bring to a boil, then reduce the heat to low. Cover the pan and let the curry simmer for about 45 minutes, stirring occasionally.
5. Add Potatoes (Optional): If using potatoes, add them to the pan after 20 minutes of simmering. Continue to cook until both the lamb and potatoes are tender.
6. Adjust Seasoning: Taste and adjust the seasoning with more salt or spices if necessary.