First, cut the butter into small pieces & leave to soften at room temperature for 30 minutes – 1 hour.
Next, place the butter, tahini, both the sugars & the vanilla into the bowl of a stand mixer. With the paddle attachment, mix on a medium speed until fully combined, no more than 2 minutes. It’s important not to incorporate too much air at this stage as it will affect the texture of the baked cookie.
With the mixer still running, add in the egg & yolks & mix to combine.
Sift together the flour, cocoa powder, baking powder, bicarbonate of soda & salt, add into the cookie dough and mix on a low speed until just combined.
Roughly chop up the white chocolate then stir through the cookie dough. Refrigerate for 30 minutes, to firm up.
In the meantime, place the granulated sugar & sesame seeds into a bowl & stir to combine.
Once the cookie dough has firmed up slightly, use a cookie scoop to portion into 12 portions, each will weigh around 85 grams.
Flatten a ball of cookie dough in your hands, place a scoop of cheesecake in the middle then wrap the cookie dough around & shape into a ball. Repeat with the remaining dough.
Next, roll each ball of cookie dough in the sesame seed sugar, making sure that they are completely coated then place into a container & refrigerate overnight
The next day, preheat an oven to 180°c/160°c fan (355°f/320°f).
Place 3-4 balls of cookie dough onto a lined baking tray, making sure that there’s plenty of room between them.
Bake for 12-13 minutes, until the edges have set but the centres are still soft.
Using a large, round cookie cutter, scoot each cookie into a perfect round shape (this step is optional but makes the cookies more uniform).
Sprinkle each cookie lightly with Maldon salt then leave to cool completely on the tray.
Repeat the cooking process with the remaining cookies, baking 3-4 cookies at a time.