Mix together the buttermilk and cream, cover, and let sit on the counter for 2-4 hours.

Once the cream and buttermilk have thickened, stir in the fresh dill, and let infuse for an hour.

In a large heavy-bottomed skillet, heat the olive oil until it shimmers. Add the onion and cook, stirring occasionally, until the onions just begin to brown, about 5 minutes.

Once the onions are cooked, stir in the coriander, cumin, turmeric, and cayenne, and cook, stirring constantly, for about 1 minute.

Stir in the mushrooms and about 1/2 cup of water. Cover, lower heat, and simmer for about 5 minutes.

Stir in the peas and potato pieces. Cover and simmer until hot, about 5-10 minutes.

Taste and add salt, a teaspoon is about right.

Pour in the dill-cream sauce and stir until combined.