In a large bowl, beat together the butter, vegetable oil, white sugar and brown sugar until smooth and creamy. Next add egg, vanilla, salt, bicarb soda and cream of tartar then mix with an electric mixer until slightly fluffy. With a spoon, gradually stir in flour until well blended. Stir in Cornflakes, oats, coconut, walnuts and chocolate chips. Drop by heaping tablespoonfuls onto ungreased baking trays, 5cm apart.
Bake in a preheated oven for 12 minutes or until slightly brown. Remove from oven and allow biscuits to cool 5 minutes on baking trays before removing to wire racks to cool completely.