Place two chopsticks or two wooden spoon handles parallel to each other a few inches apart. Place potato, widest side down, between chopsticks. Use sharp knife to cut deep slits, about 1/4-inch apart, crosswise into potato, cutting most of the way down, but not all the way through, using chopsticks as a guide. In small bowl, stir melted butter and taco seasoning mix together. Brush potato all over with spiced butter, making sure to get some butter into cuts. Place on cookie sheet.