Preheat oven to 350°F.

Melt chocolate and margarine, then combine with sugar, flour, vanilla, salt, and eggs. Blend with electric mixer on low until thoroughly mixed.

Spread mixture into a greased 13"x9" baking pan.

Bake for approximately 35 minutes - until a toothpick stuck in the centre of the pan comes out clean.

Allow bars to cool completely in the pan on a cooling rack.

Combine icing sugar, water, and peppermint extract to make the icing.

The icing needs to be drizzled over the cooled bars, so consistency may need to be adjusted. If the icing is too watery, add a little more icing sugar; if the consistency is too thick, add a little more water.

Stir green food colouring into the icing until you are happy with the colour.

Use a spoon to drizzle icing back and forth, up and down all over the cooled bar mix.

Allow icing to set by placing the pan in the refrigerator. Cut into bars.