Heat the olive oil in a skillet that can safely be placed under the broiler. Add the shallots and cook over very low heat stirring occasionally for 5 minutes, or until softened. Add the mushrooms and cook, stirring frequently, for an additional 4 minutes. Add the spinach, then increase the heat to medium and cook, stirring frequently, for 3-4 minutes, or until wilted. Reduce the heat, then season to taste with salt and pepper and stir in the slivered almonds.
Beat the eggs with the parsley, water and salt and pepper to taste in a bowl. Pour the mixture into the skillet and cook for 5-8 minutes, or until the underside is set. Lift the edge of the tortilla occasionally to let the uncooked egg run underneath. Meanwhile, preheat the broiler to high.
Sprinkle the grated cheese over the tortilla and cook under the preheated broiler for 3 minutes, or until the top is set and the cheese has melted. Serve, lukewarm or cold cut into thin wedges.