Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking dish.

In a large bowl, cream together 1 cup sugar and 1/2 cup of softened butter until smooth. Beat in eggs one at a time, then stir in the chocolate syrup. Stir in the flour until just blended. Spread the batter evenly into the prepared pan.

Bake for 25 to 30 minutes in the preheated oven, or until top springs back when lightly touched. Cool completely in the pan.

In a small bowl, beat the confectioners' sugar, 1/2 cup butter or margarine and creme de menthe until smooth. Spread evenly over the cooled brownies, then chill until set.

In a small bowl over simmering water, or in the microwave, melt the remaining 6 tablespoons of butter and the chocolate chips, stirring occasionally until smooth. Allow to cool slightly, then spread over the top of the mint layer. Cover, and chill for at least 1 hour before cutting into squares.