In large saucepan, cover potatoes with cold water and add 1 tablespooon salt. Boil, and cook until potatoes are tender about 20 minutes. drain. Meanwhile, place spinach, parsley, chives, and chervil in another saucepan. If the greens are still wet from the rinsing you do not need to add water, if they are dry add some water. Add salt to taste and cook uncovered for 10 minutes or until greens are limp. Mash the potatoes with the greens, stir in the butter, pepper, and nutmeg. Beat in the milk. Serve at once.