In a the bowl of a stand mixer fitted with the paddle attachment OR in a large mixing bowl with a wooden spoon, cream the butter and granulated sugar.
Add the powdered sugar and mix well. Then add the vanilla and plant milk and mix well to combine.
Now add the flour and baking powder and mix until it forms a dough. If you need a teaspoon or 2 more plant milk to form a dough, add it here.
Form the dough into a flat disc, wrap with plastic wrap and place in the refrigerator to chill for at least an hour, but it can chill for up to 3 days.
Preheat oven to 375* F. Line a baking tray with parchment.
Remove dough from the refrigerator. Lightly flour your work surface as well as the rolling pin.
Roll dough out to about ⅛ of an inch thickness. Use cookie cutters to cut cookies out and transfer the cookies to the baking sheet leaving about 1 inch of space between each cookie.
Press the cookie dough scraps back into a disc, wrap with plastic wrap and place back into the refrigerator.
If you want to decorate with colored sugar, cinnamon or turbinado sugar, sprinkle the cookies with them now. If you want to ice the cookies with royal icing, leave them plain. Bake the cookies in a 375* oven for 12-15 minutes or until the edges are just golden brown.
Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Repeat with remaining cookie dough.
Cool completely before decorating. Store in an airtight container at room temperature for 3 days.