Mix the garlic, coriander and the chili powder along with salt and place it aside.
Pour about 2 tablespoons of oil in a pan and heat. Add mustard seeds and urad dal. The mustard seeds will split and the oil may spill. Be careful when you are doing this. Wait until the mustard seeds stop making any noise. Add onions and fry until the onions turn brown. Add the vegetables, the mixture of step 1 and the crushed tomatoes.
Fry for about 5 minutes, if you are using canned vegetables. Otherwise cover the pan and let the vegetables cook. (This might take about 10-15 min.)