Step 1

Heat oil in a large skillet over MED HIGH heat. Season chicken thighs with salt and pepper, then add to the skillet once hot. Sear chicken 2-3 minutes per side, until very browned. Remove to a cutting board and slice into 1 inch pieces.

Step 2

Add onion, serrano, tomato paste, garam masala, tumeric, smoked paprika, cumin and sugar to same skillet over MED HIGH heat. Cook 3-4 minutes, until onion is soft and slightly browned at the edges.

Step 3

Stir in garlic and ginger and cook another 30 seconds or so. Add 1/4 cup of water or chicken broth to scrape up any browned bits in the skillet.

Step 4

Transfer skillet contents to bottom of slow cooker. Top with diced chicken and tomato sauce, stirring well to combine.

Step 5

Cover and cook on LOW 3 hours.

Step 6

After 3 hours, remove 1/2 cup of sauce from the slow cooker and slowly pour it into the yogurt, while whisking quickly. This tempers the yogurt so it doesn't curdle.

Step 7

Stir all yogurt into the slow cooker and let sit, covered, for 5 minutes. Stir in cilantro and serve.