Place chicken breasts in a large saucepan. Cover with cool water and sprinkle in 1 tablespoon of salt. Bring to a boil, uncovered, and then turn off the heat, flip chicken breasts over, and cover. Allow breasts to poach until they have an internal temperature of 74°C (165°F), about 10 minutes. Remove from pot and set aside.

Meanwhile, finely grind walnut halves until they have a consistency of wet sand and transfer to a bowl. Grate in 4 cloves of garlic. Add blue fenugreek, cinnamon and cayenne pepper. Stir to combine and set aside.

In a large skillet over medium heat, heat one tablespoon of oil until shimmer and add onion. Sautee until softened and lightly translucent, about 5 minutes.

Add the walnut mixture and cook until very fragrant, about 30 seconds to 1 minute. Pour in chicken stock, stir, and bring to a simmer. Simmer until slightly thickened and reduced, another 5-10 minutes.

Slice chicken breast and add them to the skillet. Cover in the sauce and turn off the heat. Allow to come to room temperature before transferring to an airtight container and refrigerating for at least four hours and preferably overnight. Serve cold.