In a mixer bowl, add butter and tahini. Mix with whisk attachment until combined.
Add in both sugars and whisk until fluffy. Add in egg until combined.
Switch to paddle attachment and add in flour, baking soda and salt.
Remove bowl from stand, and lightly hand mix in nutella. Do NOT mix all the way.
Scoop cooking dough onto a baking sheet with a silicone mat using an 1 and ½ tablespoon scoop. Sprinkle with flaky sea salt.
Bake for 10 minutes. Cool on sheet for 5 minutes. Transfer to cooling rack until cooled completely.
Store in an airtight container at room temperature for up to 3 days.
Notes
I strongly recommend using Nutella. I tried this recipe using my grocery store's brand of hazelnut spread and found it too liquidy. It made the cookies flat and crispy instead of soft and chewy.
Love the taste of tahini? If you want a stronger tahini taste, refrigerate your dough for 30 minutes before baking. It helps the dough develop a strong tahini flavor.
Nutritional information for this recipe is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed. Please calculate your own nutritional information if you want it exact to what you make and use my calculations as a guide only.