Line an 8"x8"x2" pan with parchment paper so it overhangs the edges of the pan. Or, you can line the pan with foil and butter the foil. Set pan aside.
Bake the potato in the microwave by pricking the skin several times with a fork. Cook on high for 3 to 5 minutes (depending on the strength of your microwave). Or you can bake the potato in your oven.
Cool the potato and peel. Then mash the potato with the liqueur, mixing until smooth.
In a 2 quart glass bowl melt the coconut oil and chocolate by cooking in the microwave on high for about 1 minute, stir for 30 seconds. If all the chocolate hasn't melted, zap it in the microwave for another 15 to 20 seconds. Stir until smooth.
Stir the potato mixture into the chocolate mixture.
Then slowly add the powdered sugar. Stir or knead with your hands until smooth.
Press the mixture into the prepared pan then score the top into 36 squares.
Press one walnut piece into the top of each square.
Chill for at least 5 hours.
Remove pan from refrigerator and lift the fudge from the pan using the paper overhanging the edges.
Using the scored lines as a guide, cut the fudge into 36 pieces. I used a long sharp knife run under very hot water. The fudge cut easily this way.
Set on a serving tray and let your guests enjoy!