Add the butter, vanilla, cocoa, and both granulated and light brown sugar to the bowl of a stand mixer. Stir on medium speed until combined, about 1 minute. Add the egg, instant espresso powder, flour, salt and baking powder to the mixer. Stir on low until it all comes together, about 1 minute.
Remove the bowl from the mixer and add the chocolate chips and cup sea salt caramel baking truffles. Use a spatula to stir by hand.
Using a small ice scream scoop, scoop the dough onto a baking sheet lined with parchment paper. Chill for 15 minutes while the oven preheats to 350°.
Once the oven has preheated, evenly space the cookies on a baking sheet and cook for 9-10 minutes, or until the edges are set and center is still soft. Remove from the oven and let cool on the cookie sheet for 2 minutes. Remove and add to a cookie rack, and sprinkle with flaky sea salt!