Cheese and Nut Loaf

2 tablespoons unsalted butter, plus more for pan
1/2 ounce dried porcini mushrooms
1 1/2 cups walnuts
1/2 cup cashews
1 yellow onion, finely chopped (1 cup)
2 teaspoons minced garlic (2 cloves)
3 ounces shiitake mushrooms, finely chopped (1/2 cup)
1 1/2 cups COOKED brown rice
2 tablespoons chopped fresh flat-leaf parsley
1 tablespoon chopped fresh marjoram
2 teaspoon chopped fresh thyme
1 teaspoons chopped fresh sage leaves, plus
    more for garnish
4 large eggs, lightly beaten
12 ounces Gruy