Step 1

In a medium bowl, stir together the flour, hot chocolate mix, baking powder, cinnamon, and salt. Set aside.

Step 2

In a large bowl, use an electric mixer to beat the butter, granulated sugar, and brown sugar on medium-high speed until well-combined and smooth, about 2 minutes. Add the egg and egg yolk and beat until combined. Add the vanilla extract. Scrape down the sides and bottom of the bowl with a rubber spatula. On low speed, gradually add the flour mixture. Fold in the chocolate chips with a rubber spatula. Chill for about 1 hour, or until the dough is no longer sticky.

Step 3

Meanwhile, preheat the oven to 350°F. Line baking sheets with parchment paper.

Step 4

Using a spoon or a medium spring-loaded cookie scoop, drop 1 1/2-tablespoon sized balls of dough onto the prepared baking sheets.

Step 5

Bake for about 10 minutes. Remove from oven and top each cookie with a piece of semisweet chocolate and 1 marshmallow half, cut side up. Return to oven and continue to bake for another 4 minutes, or until the marshmallow begins to melt slightly. Remove from the oven and use a kitchen torch to toast the tops of the marshmallows. Alternatively, place the cookies under the broiler for about 30 seconds to toast the marshmallows. Be careful as the marshmallows can go from toasted to burnt very quickly!

Step 6

Let cool on baking sheets for 5 minutes before removing to wire racks to cool completely.

Step 7

Cookies are best served the day they are made due to the marshmallow but may be stored in an airtight container in one flat layer for up to 3 days.