Makes 48 cookies
For the cookie dough:
For the chocolate-peppermint filling:
1) Adjust oven rack to the middle position and preheat oven to 350 degrees f. Line 2 large baking sheets with parchment, set aside.
2) In a medium bowl, combine flour, salt, baking soda and baking powder. Add 12 T. butter and sugar to the work bowl of a stand mixer. Using the mixer's paddle attachment, cream the butter and sugar together until light and fluffy, anywhere from 3-6 minutes (alternately you can mix the dough by hand too.) Beat in the cream cheese, then the egg, vanilla and peppermint extracts. Add the dry ingredients and mix until combined.
3) Measure dough out into 1 1/2 teaspoon portions, rolling into little balls between your palms. Place 1 1/2 inches apart on the baking sheet, dividing the cookies between the two baking sheets. Dipping your thumb in a little water, press your thumb into the dough balls to make the thumbprint. Bake the cookies - one sheet at a time. For 10 minutes, until the cookies are just set and barely beginning to brown at the edges. Remove cookie sheet from the oven, using a metal teaspoon, re-indent the cookies. Continue baking the cookies until they're light golden-brown, about 10 minutes longer. Cool the cookies on the baking sheet for about 3 minutes then transfer the cookies to a wire rack to cool completely before filling. Repeat baking steps with the second cookie sheet.
4)
To fill the cookies: Add chocolate chips, cream and butter to a small bowl. Microwave for 40 seconds until the chocolate chips are just melted, stir (continue to microwave in 10 second increments if needed). Add the corn syrup and peppermint extract, mix well. Spoon a generous 1/2 t. of chocolate into each cookie. Immediately add the sprinkles (if using).