About butter: You can use dairy butter as is listed on the package. I have done that before and it, of course, works great. If you aren't eating dairy then I suggest several options: 1) use organic non-hydrogenated vegetable shortening made from coconut oil and red palm oil or 2) use organic unrefined, extra virgin coconut oil. You can use vegan "buttery sticks," but I prefer the other options. You will use the same amount of vegetable shortening, but a little less of the coconut oil because otherwise they end up a little too oily. (This is true for almost every recipe when subbing coconut oil for butter.) For this, I used Nutiva organic vegetable shortening. It worked great!
About eggs: gluten-free egg substitutes can be used in place of eggs. Use the appropriate amount to equal 1 large egg. If using ground flax seed, you may need to add a little more water. The cookies will have a slightly different texture.
Variations:
Triple Ginger Spice
Add 4 Tbsp. unsulphured molasses, ¼ cup crystallized ginger, 1 Tbsp. fresh grated ginger, 2 tsp. ground ginger, and 1 tsp. ground cinnamon to the dough. Chill until firm enough to roll into balls. The molasses makes this dough quite a bit stickier, but also very soft and chewy. Fill with mango ice cream or sorbet.
Cacao Nib
Add 6 Tbsp. cocoa powder and ¼ cup cacao nibs to dough, plus a few tablespoons of water so the dough is soft and pliable, and not crumbly. Fill with cherry-vanilla ice cream.
Toasted Coconut
Add ½ cup toasted, unsweetened shredded coconut to the dough. Fill with pineapple-coconut ice cream or sorbet. Roll in toasted shredded coconut or finely chopped macadamia nuts.
Matcha Vanilla Bean
Add 2 tsp. matcha powder (or more to taste), 1 vanilla bean, seeds scraped, to the dough. Fill with vanilla bean ice cream.