In a medium bowl, whisk together the flour, baking soda, and salt. In the bowl of a standing mixer with paddle attachment, beat butter and peanut butter until smooth, about 90 seconds. Add sugars and beat until smooth and fluffy. Beat in vanilla and egg. Add flour in three batches, stirring just until combined.
Lay a sheet of plastic wrap on a clean work surface. Turn dough onto plastic wrap and shape into a 2-inch round log. Seal in plastic wrap and refrigerate 1 hour or overnight (or freeze–fully thaw before continuing). Heat oven to 350 degrees. Place sugar into a shallow bowl. Slice dough into ½ inch pieces and roll into 1-½ inch balls. Roll balls in sugar, then place onto parchment or silpat lined baking sheets. Gently flatten balls so they are about ¾ of an inch thick. Bake about 15 to 18 minutes (they lightly browned on the bottom). Remove from oven and quickly (but gently) press a chocolate kiss into the center of cookies – they will crack a bit. Return cookies to oven for 1 minute. Cool on wire racks for about 10 minutes, then carefully remove cookies from pan to racks to cool completely.