Melt the butter and semisweet chocolate together in a bowl in the microwave. 1. In a small bowl, stir together 1/4 cup of the tahini and the powdered sugar. Set aside.
Melt the butter and semisweet chocolate together in a bowl in the microwave. 1. In a small bowl, stir together 1/4 cup of the tahini and the powdered sugar. Set aside.
In a large bowl, whisk the eggs and sugars for about a minute. Add the vanilla, the remaining tahini and the reserved butter and melted chocolate mixture. Stir in the dry ingredients. Mix until just combined then pour into the prepared pan.