Take butter out of the fridge about 45 minutes before baking to allow it to come to room temperature.
Preheat your oven to 375° F (190° C).
Add 1 cup softened vegan butter, 1 cup of sugar, and 2 teaspoons of vanilla extract to a mixing bowl and beat with an electric mixer for 2 minutes until the butter and sugar are light and fluffy.
Slowly add 1 3/4 cups of spoon-measured flour, 2 tablespoons of cornstarch, and 1/4 tsp salt to the butter and sugar mixture and beat on low until combined.
Fill your piping bag with about 1 cup of dough at a time and pipe the dough onto an ungreased cookie sheet about 2 inches apart.
Bake the cookies at 375°F (190° C) for 9 -10 minutes. (They will still look doughy on the top but will be slightly brown on the bottom. If you start to notice the edges turning brown, take them out of the oven immediately.)
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a flat surface to cool completely.
Once the cookies are cooled, melt 1 cup of vegan chocolate chips with 1 tablespoon of vegan butter. Melt the chocolate by putting it in the microwave for 1 1/2 minutes stirring well and microwaving it again in 30-second increments until it's completely melted. You can also melt the chocolate in a double boiler.
Dip a side of the cooled cookies into the melted chocolate, scrape off any drips, and set them on parchment paper. While the chocolate is still melty add sprinkles or crushed candy canes, then allow them to cool until the chocolate hardens completely.
Notes
Vegan butter cookies can be a little tricky since there is a big variation in the quality of vegan butter. Depending on the type of butter you use, the cookies will come out a little differently. I highly recommend a stick version like Country Crock Plant Butter, Mikayo vegan butter, or Earth Balance sticks. Tub butter has higher water content and can make the dough too soft to hold its shape.
Since the butter can change the dough a lot, I recommend piping 2-3 cookies and baking them to test and make sure that they hold their shape before piping out a whole batch.
If your cookie dough is too soft and your cookies flatten when cooked, add 1 tablespoon more flour to the dough.
If your dough is too firm to press through your piping bag, you will need to add an additional tablespoon or two of vegan butter to the dough.
Be sure to spoon measure the flour so that you have the proper flour to butter ratio.