In a large skillet, melt 1 tablespoon of the butter over medium heat until it stops foaming. Add half of the shallots and cook until lightly browned. Add half of the mushrooms and saute over medium-high heat until theyve softened and their liquid has evaporated, about 5 minutes. Transfer the mushrooms to a plate, then repeat with the remaining butter, shallots and mushrooms. Return the reserved mushrooms to the skillet, stir in the chopped mixed herbs and saute for another minute or two.
Meanwhile, toast the bread. Stir the cream into the mushroom mixture and season with salt and white pepper to taste. Butter the toast, if you like, and divide the mushroom mixture evenly over each slice; serve immediately.