Step 1

In large saucepan, melt 2 tablespoons butter over medium heat. Add onion, garlic, ginger, and serrano and cook, stirring and scraping bottom of saucepan frequently with wooden spoon, until mixture is softened and onion begins to brown, 5 to 7 minutes.

Step 2

Add garam masala, coriander, cumin, and pepper and cook, stirring often, until fragrant, about 1 minute.

Step 3

Add water, tomato paste, sugar, and salt and scrape up browned bits on bottom of saucepan. Whisk until no lumps of tomato paste remain. Bring to a boil. Turn off heat and slide saucepan to cool burner.

Step 4

Stir in cream and let cool slightly. Tip saucepan to one side and use immersion blender to carefully process sauce until smooth, 30 to 60 seconds, making sure to keep head of blender and blade completely submerged (ask an adult for help). (If you don’t have an immersion blender, carefully transfer sauce to blender jar [ask an adult for help]. Then, hold lid firmly in place with folded dish towel and process until smooth. Return sauce to saucepan.)

Step 5

Add chickpeas to saucepan and bring to simmer over medium heat (small bubbles should break often across surface of mixture). Cover saucepan with lid; reduce heat to low; and cook, stirring and scraping bottom of pan occasionally, for 15 minutes.

Step 6

Turn off heat. Use oven mitts to remove lid. Add 2 tablespoons cilantro and remaining 2 tablespoons chilled butter. Stir until well combined and butter is melted. Serve, sprinkling individual portions with remaining 1 tablespoon cilantro.