Cut 5 Roma tomatoes into quarters and lightly pulse in a blender. You want them to be in very small pieces, but no fully blended.
Add the blended tomatoes to a large pot along with 1/2 cup of water and 2 tablespoons of Shan masala. Mix, cover, and set on medium-high heat.
Peel a medium russet potato and cut into thin rounds. If the middle of the potato is thick, you can cut in in half first and then slice into thin half circles. Mix the potatoes into the pot, cover again, reduce to medium heat, and let them simmer for 25-30 minutes, or until the potatoes are soft. Stir periodically to ensure that it does not burn.
Cut 1.5 pounds of chicken thighs into 1 to 2 inch pieces. Place a large pan on high heat and add some oil. Once the pan is hot, add the chicken and then sprinkle it with salt, pepper, and another 2 tablespoons of Shan masala. Allow the thighs to fry until golden on each side, and then reduce to medium heat until they are cooked through. Remove from heat once fully cooked.
Cut up 1/4 of a large white onion into thin pieces and 1/2 of a jalapeño into thin slices. Unless you want a lot of heat, deseed your jalapeño. Add the onion to a medium sized pan on medium high heat with some oil and let it fry, stirring periodically until golden brown. Add the jalapeño in for the last 2 minutes and allow it to lightly sear on both sides.
Once your potatoes are done cooking, add in 2 teaspoons of freshly squeezed lemon juice, 1/2 teaspoon of ginger paste, 1/2 tablespoon of chopped cilantro, and the fried onion and jalapeño along with its oil. Stir well and then ad into your chicken and fold it in. Cover again and allow it to simmer for at least 5 minutes.
Plate this with some white basmati rice and top it with additional cilantro.Enjoy!