Cookie Preparation

• In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter, granulated sugar, and brown sugar together on medium high speed until fluffy and light in color, about 3 minutes.
• Add the egg and vanilla extract, and then beat on high speed until combined. Scrape down the sides and bottom of the bowl as needed.
• In a separate bowl, whisk the flour, cocoa powder, hot cocoa mix, baking soda, and salt together until combined.
• Add the dry ingredients to the bowl with the wet ingredients. Beat on low until combined, then beat in the milk.
• Cover dough tightly and chill in the refrigerator for at least 2 hours and up to 3 days.
• Preheat oven to 350°F (177°C). Line large baking sheets with parchment paper.
• Remove cookie dough from the refrigerator. Scoop and roll dough into balls, arranging them on the baking sheets.
• Bake the cookies for approximately 10 minutes. Press a marshmallow half into the top of each cookie and return to the oven for an additional 2 minutes.
• Cool cookies on the baking sheet for 10 minutes, then transfer to a wire rack to cool completely.
• Melt the chocolate in a double boiler or microwave, then spoon melted chocolate over each cooled marshmallow-topped cookie.
• Cover leftover cookies tightly and store at room temperature for up to 1 week.