Melt butter in a large skillet on high heat. Add the mushrooms, garlic and shallots, and sprinkle lightly with salt and pepper. Sauté for 5 minutes stirring frequently.
While the mushrooms are cooking, heat a small skillet on high heat. Add the pine nuts. Cook, stirring frequently, until they begin to get a little toasted. As soon as they begin to toast, remove the pan from the heat and put the pine nuts into a small bowl. Set aside.
Put mushroom mixture in a bowl, add the toasted pine nuts. Once the mushrooms have cooled down a bit, mix in the lemon juice, sour cream, and parsley.
Serve warm or chilled, with endive leaves or on baguette slices.