Cook rice till cooked and slightly sticky (white rice, I use basmati will take approx 20 min), & lentils till soft. Cool slightly. Finely mince a medium sweet potato, which has been peeled, and cook until soft. Cool slightly. Finely chop the mushrooms. Spinach leaves should be rinsed and finely shredded. Mix all ingredients and spices together adding salt & pepper to taste. Chill in the refrigerator 15-30 min. Form into patties and sauté in pan or can be done on a vegetable grill on an outdoor grill. Make sure to grease or spray pan as these burgers will tend to stick.