3 cups spinach, rinsed and stemmed
6 (4-6 oz.) fresh boneless, skinless chicken breasts
1/4 tsp. ground black pepper
2/3 cup ricotta cheese
2 tsp. brown mustard
1/3 cup finely chopped pistachio nuts
2 tsp. chopped fresh basil
1 clove garlic, crushed
1/4 pound cherry tomatoes, halved

Preheat oven to 350°F. Lightly oil a 11×7-inch baking dish; set aside. Steam spinach until wilted; drain, rinse under cold water, and drain again. Pat dry and flatten out with paper towels. Flatten chicken breasts between sheets of wax paper to 1/4-inch thickness with a mallet or rolling pin. Season with pepper. Cover each breast with a layer of spinach. In a medium bowl, combine ricotta cheese, mustard, pistachio nuts, basil and garlic; spread evenly over spinach to within 1/4-inch of the edges. Roll chicken up jelly-roll style, starting from the shortest end. Arrange rolls in the baking dish, seam-side down. Cover with aluminum foil and bake until done, 18 to 24 minutes. Refrigerate for 3 hours then cut into 1/2-inch slices, if desired. Serve garnished with tomatoes.