Unwrap 24 peppermint kisses and place a bowl in the freezer.
In a large bowl, cream together the butter and sugar until light and fluffy. Mix in the egg, vanilla and peppermint extract.
In a separate bowl, mix together the flour, baking soda and salt.
Alternate between mixing the dry ingredients and the milk into the wet ingredients until fully combined.
Place the white sanding sugar into a shallow bowl.
Using a medium cookie scoop, scoop the cookie dough into your hands and roll into a ball. Roll the cookie dough ball in the sanding sugar until fully coated, then place on parchment paper lined baking sheets. Repeat with the remaining cookie dough.
Place the cookie dough balls in the fridge for at least 2 hours.
Preheat the oven to 350℉.
Place the chilled cookie dough in the preheated oven for 8-10 minutes, or until the edges are lightly brown. Allow to cool for around 5 minutes on the baking sheet before pressing in 1 frozen kiss onto each cookie. Allow to cool completely on baking sheets before storing in an airtight container.