For the Japanese Curry Powder:

• 2 tablespoons Turmeric 
• 1 tablespoon ground Indian Coriander Seed 
• 1 teaspoon ground Cumin Seed 
• 1/2 teaspoon ground Cardamom Seed 
• 1/2 teaspoon Cassia Indonesian Cinnamon 
• 1/2 teaspoon Powder Ginger 
• 1/2 teaspoon freshly ground Black Tellicherry Peppercorn 
• 1/4 teaspoon Indian Cayenne 
• 1/4 teaspoon ground Cloves 
• 1/4 teaspoon ground Fennel Seed 

For the Chicken Curry:

• 1-1/2 lb (675 g) boneless, skinless chicken thighs
• Kosher Salt Diamond Crystal and Black Tellicherry Peppercorn, ground
• 4 tablespoons vegetable oil
• 1 cup thinly sliced onions
• 1/2 cup coarsely grated peeled apple
• 2 tablespoons Japanese curry powder
• 1 tablespoon chopped fresh ginger
• 1 tablespoon chopped garlic
• 2 tablespoons all-purpose flour
• 2 cups chicken stock 
• 4 cups baby spinach
• 2 tablespoons finely chopped fresh cilantro

For the Japanese Curry Powder:  Combine all spices in a small bowl and stir until uniform. Curry powder keeps well in a sealed container.

For the Chicken Curry:  Cut chicken thighs into 2-inch pieces. Season with salt and pepper. Heat 2 tablespoons oil in a large skillet over medium-high heat. Add chicken in batches and sear for 1 to 2 minutes per side or until lightly golden. Reserve.

Reduce heat to medium. Add remaining 2 tablespoons oil and onions to skillet, and sauté for 2 minutes or until onions are softened. Add apple, curry powder, ginger and garlic and sauté for 1 minute or until fragrant. 

Stir in flour and cook, stirring, for 1 to 2 minutes to cook out floury taste. Stir in stock a little at a time until well combined. Bring to a boil, stirring. Reduce heat and simmer for 2 minutes to thicken. Taste and adjust seasoning.

Return chicken and any juices to skillet and cook in sauce for 10 minutes or until meat is cooked through. Stir in spinach and cook for 1 minute or until spinach wilts. Garnish with cilantro just before serving.