Indian Dosa with Coconut-Potatoes

Rinse rice and lentils separately in cold water and then soak, covered, in 2 bowls of water overnight.

Drain rice and lentils. In separate batches, purée rice and lentils in a food processor, adding just enough water (4 to 6 ounces) to make a fine paste. 

Mix together both purées with the sugar and 2 teaspoons salt Cover with plastic wrap and let ferment overnight at warm room temperature.

The next day, scrub potatoes and cook in a pot of boiling water, covered, until knife-tender, about 20 minutes.

 Drain cooked potatoes and cool briefly. Peel and chop into cubes.

Rinse scallions, pat dry and finely chop. 

Heat 3 tablespoons oil in a pan and fry the mustard seeds over high heat until they start to pop, about 15 seconds.

Add coriander seeds and scallions to pan and cook over low heat, stirring occasionally, 3-4 minutes.

Mix together ground spices, potatoes and coconut milk in the pot.  Season with salt and pepper. Cover and cook over medium heat for 10 minutes. Mash the potatoes. Keep warm.

Briefly stir the fermented batter. It should be like a thin pancake batter; if necessary, thin with a little warm water. Lightly coat a heavy non-stick pan with oil and heat over medium heat.