In a mixing bowl, whisk together Greek yogurt, garam masala, smoked paprika, ground cumin, minced garlic, minced ginger, and salt until smooth. Add the boneless chicken thighs, ensuring they are fully coated in the marinade. Cover the bowl with plastic wrap and refrigerate for at least 1 hour—overnight if possible.

Heat two tablespoons of oil in a large skillet over medium-high heat. Add the marinated chicken thighs, cooking for about 5-6 minutes per side until golden brown and slightly charred. Remove from skillet and set aside.

In the same skillet, add more oil if needed, then add diced onions. Sauté for 5-7 minutes until golden brown and soften. Add minced garlic, ginger, ground cumin, and smoked paprika, and cook for an additional 2 minutes until fragrant.

Stir in the tomato puree, allowing it to simmer on low heat for about 10 minutes until the sauce thickens. Use an immersion blender to puree the sauce until smooth.

Reduce the heat and stir in the heavy cream. Add seared chicken back into the pan, ensuring each piece is submerged in the creamy sauce. Simmer on low for an additional 15 minutes.

Garnish with freshly chopped cilantro and serve hot alongside basmati rice or naan bread.