Stew the mutton ahead of time, preserving two cups of the broth, then refrigerate.
Preheat oven to 350 degrees; grease a casserole dish.
Saute nuts, carrots and cauliflower in 1 tbsp of butter, stirring often, until lightly cooked.
Make the rice using the broth to substitute for 2 cups of the water required. When the rice is almost done, add the other ingredients, including the remaining tbsp of butter, except for the mutton pieces, and cook five more minutes.
Add mutton and pour into large greased casserole or dutch oven and bake 10-15 minutes, covered. If rice is too dry add 1/4 cup water or mutton broth before baking.
Serve with Afghan bread or pita bread and cucumber yogurt salad.