Heat 2-3 cups of water in a pan over medium-high heat. Once the water comes to a boil, add sugar and stir until it dissolves.
Add spinach and green peas to the pan and cook for 2 minutes.
Remove the pan from the heat and strain the spinach and peas in a fine-mesh strainer.
Run them under cold water to stop the cooking process. Drain well.
Add the blanched spinach and peas to a blender, along with cilantro, chilies, ginger, and 1 tablespoon of water, and blend to make a smooth paste.
Scrape the sides of the blender a few times while blending.
Transfer the green paste to a medium mixing bowl.
Add potatoes, chickpea flour, cornstarch, breadcrumbs, salt, dry mango powder, and garam masala powder, and mix well.
Take a small lime size mixture and shape it to make a smooth ball. Gently press the ball and press a cashew half in the center. Shape all the kababs in the same manner.
Heat 3-4 cups of vegetable oil in a pan over medium-high heat. Once the oil is hot, reduce the heat to medium. Drop 5-6 kababs in the hot oil and fry until they turn golden brown, flipping a few times in between.
Drain on a plate lined with kitchen tissues. Fry the remaining kabab in the same manner. Serve hot.