Pick a skillet that can take heat. Something with an insulated handle is good. Put on some shabby clothes. Cooking Indian restaurant style is messy stuff.
Place the skillet over medium low heat.
Add 3 Tbsp of oil. When it starts to shimmer add the onions and cook until the edges of the onions start to colour. This should take 3-4 minutes. Add the cumin seed and green chilies and cook another 30 seconds or so.
Move the onions to one side. There should be a fair bit of oil in the bottom of the pan. Add the spice mix and stir to thoroughly coat the spices in oil. It should start to bubble a bit. Cook the spices for about 30 seconds. Watch your pan carefully. You don't want to let your spices burn.
Add the garlic ginger paste and chopped cilantro stems and stir the spices, garlic ginger paste and onions to combine. Cook about 30-45 seconds.
Turn the heat up to medium high. Add 3 oz of curry base. Stir to combine. Let cook about a minute. You should see craters forming and a bit of oil separating out.
Now add 6 oz of curry base. Stir to combine and cook about 90 seconds. You want to see the same little craters.
Add the remaining curry base. Stir to combine. Reduce the heat to medium low.
Add the eggplant, stir to combine and let simmer about 3 minutes. Then add the cherry tomatoes and let simmer another minute or two.
Garnish with a bit of chopped cilantro if desired. Serve with rice or Indian flatbreads. This makes a great vegetable side dish or vegetarian main course.