Beat first 5 ingredients, then by hand stir in the flour, powder, and soda. When it is dough, add chips and nuts. Drop by tablespoonful onto lightly greased cookie sheet and bake at 180ºC for 8-12 minute (careful not to overbake). If you want some variation, try leaving out a little margarine and replacing it with peanut butter, or replacing a little of the flour (about a cup) with oatmeal.
Notes: If the dough seems sticky, add a little flour or oatmeal until it's easier to handle. If it's too "wet," the cookies will be flat and crunchy.