Melt 1 tablespoon butter with the oil in a 12-inch skillet over medium heat. Add the ginger and garlic; cook, stirring, for 30 seconds without browning.

Add the garam masala, cumin, coriander, and Kashmiri chili powder. Stir constantly for 20 to 30 seconds, just until aromatic.

Pour in the tomato puree and water. Bring to a steady simmer and cook uncovered for 6 to 7 minutes, stirring often, until the sauce darkens slightly and a spoon drawn across the pan leaves a brief trail.

Reduce the heat to low. Stir in the cream, crushed fenugreek if using, remaining tablespoon butter, and 1/4 teaspoon salt.

Fold in the shredded chicken. Warm gently for 3 to 4 minutes, stirring once or twice, until the thickest pieces reach 165°F. Do not let the sauce boil hard.

Taste before adding more salt. If the tomato tastes flat rather than bright, stir in the lemon juice. Finish with cilantro and serve immediately.