Mise en place (putting in place). Clean and prep everything before hand.
Combine the coriander, cumin, turmeric, and cayenne in a small bowl, add about 1 1/2 tablespoons of water, and mix to make a paste.
Pour the oil in a medium skillet and place over medium heat. When hot, add the onions and stir and sauté for about 3 to 4 minutes.
Add the ginger and spice paste. Stir the ginger around three or four times, then add the spice paste and cook, stirring for about a minute.
Add the tomatoes. Stir and scrape up from the bottom of the pan for about 4 minutes. Add about 3/4 cup of water and bring to a boil. Cover, reduce heat, and simmer for about 20 minutes.
Add mushrooms. Bring back to a boil, then cover and simmer for 10 minutes.
Add the peas. Bring back to a boil and cook for about 5 minutes. Adjust salt to taste and serve with basmati rice.