Rinse off the dried morels quickly and then leave them to soak in 1½ cups water for 20 to 30 minutes or until they are quite tender; if you are using fresh, there is no need, of course, to soak them.
Drain, saving the soaking liquid as you do so. Strain the soaking liquid through a clean piece of cloth and set it aside. Cut each mushroom in half lengthwise.
Put the ginger and garlic into the container of a food processor or blender. Add ¼ cup water and blend until you have a smooth paste.
Heat the oil in a 2½- to 3-quart pot over medium heat. When hot, put in the paste from the food processor (keep face averted). Stir and fry for 1 minute.
Add the coriander, cumin, turmeric, and cayenne. Stir and fry for another minute.
Put in the minced tomato. Stir and fry for about 3 minutes, gently mashing the pieces of tomato with the back of your stirring spoon. You should end up with a relatively smooth paste.
Now put in the morels, their strained soaking liquid (or 1½ cups water, if you are using fresh morels), the peas, and the salt. Bring to a simmer.
Cover, lower heat and simmer gently for 10 minutes. Add the garam masala. Stir to mix.