Whisk together the flour, cornstarch, baking powder, and salt in a bowl. Set it aside.
2 ¼ cups (280g) all purpose flour , ¼ cup (25g) cornstarch, ½ teaspoon baking powder, ¼ teaspoon salt
In another large mixing bowl, beat the butter and the sugar together using a hand mixer on high speed until the mixture is fluffy, about 2-3 minutes.
¾ cup (170g) unsalted butter, at room temperature, ¾ cup (150g) sugar
Add the egg and the vanilla and beat for another minute or so (scrape the sides of the bowl as needed).
1 medium egg, at room temperature, 2 teaspoons vanilla extract
Gradually add the flour mixture to the egg mixture and beat on low speed until combined. It'll look crumbly (see photo in post).
If the dough is too wet, add some more flour, about a tablespoon at a time, until it all comes together.
Squeeze the crumbles together to form a large piece of dough. It's perfect when you are able to pick it up in 1 piece (see photo in post above).
Divide the dough in half. Roll out one portion of the dough between 2 sheets of parchment paper to a thickness of about ½ an inch (1.2 cm).
Put the rolled out dough in the freezer for 10 minutes, as is with the parchment paper.
Meanwhile, preheat the oven to 350°F / 180°C.
Take the dough out of the freezer and cut out circles with your cookie cutters.
Then transfer the cookies to a baking sheet lined with parchment paper and bake for 12-13 minutes. (I bake them one tray at a time.)
Re-roll the dough scraps and repeat the procedure with the other piece of dough.
Transfer the cookies to a wire rack and let them cool completely.
Melt the Chocolate
Melt the chocolate, either over a bowl of just simmering water or in the microwave in 30 second increments.
6 ounces (170g) dark semi-sweet chocolate, chopped
Place the melted chocolate in a small bowl.
Dip one half of a cookie into the melted chocolate and let excess chocolate drip off.
Place the cookie on a tray lined with parchment paper. Add the chopped nuts or your desired toppings, if using. Repeat with the other cookies. Then let the cookies sit until the chocolate sets, about 10 minutes.
For best, accurate results, weigh all the ingredients with a digital scale.
Don't overbake these cookies! They will not brown much, but baking them any longer than the suggested time will result in a hard cookie.
The number of cookies will depend on the size of your cookie cutters and how thick you make them. I used 3-inch (7.6 cm) round cookie cutters and made them ½ inch (1.2 cm) thick, which make 12 cookies.
Detailed freezing instructions are included in the post.