1. Heat oven to 350 degrees. Butter a 9 1/2-by-4 1/2-by-2 1/2-inch loaf pan, line bottom with parchment paper, and butter again; set aside. Place dried porcini in a small bowl; add boiling water to cover. Let soak 20 minutes; drain, finely chop, and set aside.

2. Toast walnuts and cashews on a baking sheet until lightly browned and fragrant, about 10 minutes. Let cool. Finely chop with a sharp knife, or in the bowl of a food processor, set aside. Increase oven heat to 375 degrees.

3. Melt butter in a saute pan over medium heat. Add onion and garlic; cook until translucent, about 3 minutes. Add shiitake mushrooms and the reserved porcini; cook, stirring constantly, until all the mushrooms are golden, about 5 minutes. Transfer to a large bowl. Stir in rice, the toasted nuts, parsley, marjoram, thyme, sage, eggs, Gruyere, cottage cheese, salt, and pepper.

4. Pour mixture into prepared pan, and bake until golden brown and firm to the touch, about 1 hour. Let cool in pan 20 minutes, then invert loaf, and remove from pan. Serve hot or warm, garnished with sage leaves.