Preheat the oven to 350 degrees. Cream together the butter, sugar, eggs, milk and vanilla in a mixer bowl. Combine the flour, baking soda, baking powder and salt in another container. Add to the butter mixture and blend well. Stir in the chocolate chips (or M&Ms) carefully so as not to break them. Cover the bowl and refrigerate overnight. Scoop out the dough by teaspoonfuls and drop on an ungreased cookie sheet, 3 cm apart. Bake until browned (about 8 minutes). Cool slightly then remove onto a rack to cool completely.