Combine the milk, buttermilk, and salt in a large pot over medium-high heat. Heat the mixture, stirring occasionally to prevent the bottom from scorching, until it reaches a gentle simmer and the curds have clearly separated from the yellowish whey.

Pour the mixture into a colander lined with a double layer of cheesecloth. Gather the edges of the cloth and wring it tightly to remove excess moisture. Place the cheesecloth bundle between two nesting plates and weight the top plate with a heavy can until the cheese is firm enough to slice, about 30 minutes.

Place the spinach and mustard greens in a large bowl and microwave until completely wilted, about 5 to 7 minutes. Squeeze out the excess liquid from the greens and chop them coarse.

Melt the butter in a Dutch oven over medium heat. Add the cumin seeds, coriander, paprika, cardamom, and cinnamon and cook until the spices are fragrant and beginning to darken.

Add the onion and salt to the pot and cook until the onion is softened and beginning to brown, about 8 to 10 minutes.

Stir in the garlic, ginger, and jalapeño and cook until fragrant. Add the tomatoes, cashews, water, and buttermilk, then stir in the wilted greens. Simmer for about 10 minutes to allow the flavors to combine.

Puree the mixture using an immersion blender until mostly smooth, or transfer to a standard blender and process until it reaches a thick, saucy consistency with some remaining texture from the greens.

Cut the pressed cheese into bite-sized cubes. Gently stir the cheese cubes and cilantro into the spinach sauce. Serve hot with rice or naan.