With racks in the middle and top half of the oven, preheat oven to 350F. Line two baking sheets with parchment paper and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and 1 c. sugar on medium speed until light and fluffy, 3-5 minutes. Scrape down sides of the bowl and beat in egg and vanilla.

Reduce speed to low and add cocoa powder, flour and sea salt. Beat until dough come together - about 2 minutes. Dough will be thick.

Use a standard size ice cream scoop to portion prepared dough into equal portions. Roll between clean palms to form a ball. Roll ball in remaining 1/4 c. granulated sugar and set onto prepared baking sheet. Continue until dough is gone, placing cookies about 1" apart on baking sheet (dough will not spread much when baked, only when Hershey kiss is added).

Bake cookies in preheat oven for 8-10 minutes, rotating halfway through. Cookies are ready when the dough is set.

While cookies are baking, unwrap about 30 Hershey kisses and set aside.

When cookies are ready, remove from oven and set cookie sheets on a wire rack. Gently press Hershey kiss into the center of the cookie and allow to cool completely before removing cookies from the baking sheet.

Store in an airtight container for up to 4 days.