If you want a dessert that's low-fat and takes no time to make, buy yourself a cantelope or something.
1 c granulated sugar
1/2 c butter
4 eggs, beaten
1 c flour
1/2 t salt
16 oz. chocolate syrup (Note: if you live somewhere civilized and reasonable, you can just buy a 16 oz. can of chocolate syrup, punch holes in the top of it, and proceed. If you live in Hayward, however, you will be stuck buying a bottle of chocolate syrup and measuring out 2/3 of it. Scowl.)
1 t. vanilla
Mix ingredients in order, pour into greased 9x13 cake pan. Bake 30 minutes at 350 degrees. Let cool 30-35 minutes.
2 c powdered sugar
1/2 c butter
2 T milk
1/2 t peppermint extract (Note: this is nasty stuff. If you've never cooked with it before, be prepared. Hooo. I am surprised more teenagers don't get drunk on peppermint extract. Don't tell me it's because it's nasty. How lately have you been to a teenage party with alcohol? They drink some stuff that's much, much nastier than peppermint extract. And not as alcoholic.)
green food coloring, if you believe that minty things ought to be green--2-3 drops should be sufficient
Mix and spread on cooled bars. Let stand a few minutes.
1 c chocolate chips
6 T butter
Melt together in microwave, being careful not to scorch. (This is where a 2 c pyrex measuring cup comes in really handy. The measuring and the melting work together. How eeeeeeasy.) Pour over the mint layer and let set. These bars may be frozen or refrigerated, but they don't have to be.