Whisk together the yogurt, besan, sugar, nutritional yeast, salt, and 2 cups of water in a bowl until perfectly smooth with no lumps of flour remaining.

Heat the butter in a large saucepan over medium-high heat until shimmering. Add the mustard seeds, cumin seeds, fenugreek seeds, cloves, cinnamon stick, and bay leaf, cooking for about 1 minute until the mustard seeds begin to pop and sizzle. Remove the pan from the heat and stir in the ginger, green chili, curry leaves, and asafetida—the mixture will spatter quite a bit, so be ready.

Pour 1 cup of water into the saucepan, return it to medium heat, and simmer for 5 minutes. This step is essential to extract the maximum flavor from the whole spices and aromatics into the liquid.

Whisk in the prepared yogurt mixture and increase the heat to medium-high until it begins to simmer. Once simmering, reduce the heat to medium-low and cook for about 10 minutes until the sauce has thickened slightly and looks creamy. Whisk occasionally to maintain a silky texture, adding a splash of water if it becomes too thick.

Turn off the heat and discard the cinnamon stick, bay leaf, and cloves. Stir in the cilantro and lime juice, then adjust the salt and sugar to your preference. Serve hot over rice or khichdi.