In a mixer fitted with a paddle attachment cream together butter and brown sugar. Add tahini.
Mix in egg and vanilla until incorporated.
Sift together flour, baking soda and salt. Mix until all dries are incorporated.
Stir in semi sweet chocolate by hand.
Scoop cookies onto parchment lined baking sheet and top with flaky sea salt. Bake at 350 degrees until edges start to brown. (About 10-12 minutes)