Cream sugars with butter. Beat in eggs. Add oil. Combine dry ingredients together, and then gradually add them to the sugar-butter mixture. Mix in vanilla extract flavor. (NOTE: This dough will seem very oily. That's normal—it uses a cup of butter and a cup of oil. Don't worry—they bake up crispy and sweet.)
Split dough into 6-8 colored groups of even-sized balls. Add food coloring to each of the dough balls until desired color is achieved. Roll each color into 10-12 balls of decreasing sizes.
Dip the bottom of a glass into granulated sugar, and press the dough balls flat using the bottom of a glass, in varying sizes. With a star cookie cutter, cut out the basic dough color with the star cutter for the number of trees you plan to make.
Start baking your largest cookies at 350º F for 10-12 minutes and less for smaller sizes. Stack the cookies with the largest cookies on the bottom, graduating to the smallest size on the top. Add a small dollop of frosting on the bottom of each star to secure in place. If you are just using the trees for decoration, use hot glue to secure the star on top.