Blend onion, garlic, tomato sauce, garam masala and salt. Put in an electric pressure cooker with soaked chickpeas and diced sweet potatoes.
ETA: I forgot ginger, which is blended with the items in the first step.
Edited with more details:
In a blender liquify onions, garlic, ginger, tomato sauce. I used two small onions, a giant clove of garlic, about 2 tbsp equivalent volume of ginger, a 500 mL jar of homemade tomato sauce (just tomato no seasoning).
Put the blended stuff and extra water to rinse the blender (if needed) in the EPC. You want enough liquid to cover the beans and potatoes. Add soaked beans (my volume soaked was about a liter, have no idea what the dry quantity was). Add peeled and diced sweet potatoes (2 lbs maybe?). I seasoned it with about 1 tbsp fresh ground garam masala and maybe half a tbsp of salt?
I cooked for 40 mins on high pressure regular heat.
Stir and taste after cooking, you will probably need more salt.
soak dry chickpeas the night before (or rinse canned ones).
fry the onions and garlic till onions are transparent.
add diced tomatoes and a teaspoon of garam masala and simmer for 10 mins.
put sauce and chickpeas and diced boiled sweet potatoes into a pressure cooker and cook for 10 mins. If you don't have a pressure cooker, slow cooking for an hour also works.
It's not correct though? I can add more detailed steps if someone wants them (and I'll edit my comment), but detailed step by step instruction isn't the intent of this community so I didn't think to provide them unless explicitly asked.
For example I pressure cook unsoaked chickpeas for like 40 minutes instead of soaking sometimes. If you're pressure cooking the onions no need to saute them first. Etc...
Add a little baking soda to your soak water to help them cook all the way through. I only cook my chickpeas for twenty minutes when they've been treated this way.