Make the pâté:
Butter loaf pan, then line bottom and sides with parchment paper and butter paper.
Bring stock to a boil in a small saucepan. Remove pan from heat, add porcini, and let soak in hot stock until softened, about 30 minutes.
With a slotted spoon, transfer porcini to a medium-mesh sieve set over a bowl. Press on porcini with back of a spoon to remove excess liquid, then add this to soaking liquid and reserve. Rinse porcini to remove any grit. Pat dry, chop, and put in a large bowl.
Strain reserved soaking liquid through a fine-mesh sieve lined with a coffee filter or dampened paper towel into another small saucepan. Bring to a brisk simmer over moderate heat and simmer until reduced to about 1/4 cup, about 10 minutes. Add to porcini.
Put a rack in middle of oven and preheat oven to 350°F. Heat 2 tablespoons butter in a large nonstick skillet over moderate heat until foam subsides. Add shallots and garlic and cook, stirring, until softened, about 6 minutes. Add sherry and cook, stirring for 1 minute. Transfer mixture to a blender. Heat 2 more tablespoons butter in skillet over moderately high heat until foam subsides. Add one third of shiitake and oyster mushrooms and cook, stirring, for about 2 minutes. Transfer to a bowl and cook remaining mushrooms in 2 batches, adding 2 more tablespoons butter to skillet for each batch. Add 2 cups sautéed mushrooms to shallot mixture in blender, and add remaining mushrooms to porcini mixture.
Add cream, then eggs and almonds to blender and purée until mixture is very smooth, about 1 minute. Add purée to porcini mixture and stir in parsley, thyme, bread crumbs, lemon juice, salt, and pepper until well combined. Pour mixture into loaf pan and cover with foil.
Put loaf pan in a larger baking pan and add enough boiling water to reach halfway up sides of loaf pan. Bake until set 1/2 inch from edges, about 50 minutes (pâté will not be completely set in center). Remove loaf pan from baking pan and let cool to room temperature on a rack. Refrigerate pâté in loaf pan, covered, for at least 6 hours. Bring pâté to room temperature before adding topping.
While the pâté comes to room temperature, make the topping:
Heat butter and oil in a large skillet over moderately high heat until foam subsides. Add mushrooms and almonds and cook, stirring, until mushrooms are tender and liquid they give off has evaporated, 6 to 8 minutes. Transfer to a heatproof bowl and let cool, then add parsley, salt, and pepper and toss to combine.
To unmold pâté, run a thin knife between paper and edges of loaf pan. Invert a large plate over loaf pan and invert pâté onto plate (peel off paper). Mound topping on pâté, and spread on toasts and/or crackers.
