Place the flour, cocoa, sugar, xantham gum, soda, salt, and instant coffee in to your kitchen aide mixing bowl. Use a whisk to mix the ingredients well.
Cut up your butter and margarine and put into the mixing bowl. Use your paddle attachement and mix on low for a minute. Then add the vanilla, cream and milk and mix until it is a soft dough. Divide the dough in half. Use your hands to shape each piece of dough into a round ball.
Place a piece of wax paper on rolling mat and then place one round ball of dough ontop of the wax paper. Place a second piece of wax paper ontop of dough. Use your rolling pin and roll out the dough to 1/4 inch thickness. I have a great rolling pin that has rings you can put on the end to make it easy to roll out the exact depth (take a look at end of recipe if you are interested).
Place the rolled dough, still between the wax paper, in the fridge.
Repeat with second ball of dough. Chill dough for 45 minutes.
Remove one piece of dough from the fridge, leaving the wax paper on, and place it ontop of your mat. Gently pull off the top piece of wax paper.
Take your shamrock cookie cutter (or round if you don't have a shamrock!) and cut out as many as you can.
Place the cookie shamrocks on a parchment lined baking sheet.
Bake in a 350 degree F oven for 10-12 minutes. Remove from oven and place baking sheet on cooling rack for 10 minutes. Then transfer cookies to cooking rack to cool completely.
If you have enough baking sheets, you can cut out both pieces of dough. If you do not have enough baking sheets, then let your baking sheets cool and then repeat with your second round of dough.
If you don't have a shamrock cookie cutter, you can use a round cookie cutter, and they look nice as well.
Place your white chocolate in a bowl. In another small bowl, heat the cream in a microwave for 20-30 seconds. Then pour the cream onto your white choclate and let it sit to melt. Then add 7 drops of green food coloring and stir. Then add the icing sugar and stir. You can add more cream or icing if you need to adjust the texture. It will thicken as it cools.
Put the green 'icing' into a decorating bag or a ziploc bag. Cut a small corner out of bag and gently squeeze the 'icing' onto the bottom of one cookie and then line up the bottom of the second cookie and gently press together. You can also use a spoon or knife and just spread teh icing on.
These cookies are great, as this icing does not make the cookies soft or mushy. You can put all the icing in and have them made, or let your kids do thier own. You also can put as much or as little 'icing filling' in as you like.