Step 1

Preheat the oven to 350ºF. Line with parchment, and lightly grease the inside of an 8” square or round baking dish with parchment.

Step 2

Melt the butter and chocolate together in the microwave, or in a heat-proof bowl placed over a small pot of boiling water (a double boiler). Remove from the heat, and allow the chocolate to cool.

Step 3

In a large bowl, mix together the cooled melted chocolate, sugar, brown sugar, and salt. Add the eggs, one at a time, mixing each one until fully incorporated.

Step 4

Sift together the cocoa powder and potato starch into the chocolate mixture. Beat the batter vigorously with a wooden spoon for a few minutes until it starts to look shiny, and pulls away from the sides of the bowl. Transfer the batter into the greased baking dish.

Step 5

Dollop the top with spoonfuls of chilled tahini, then using a skewer or knife, swirl the tahini in one direction through the batter. Swirl the tahini in the opposite direction to create a pattern.

Step 6

Bake for 22-25 minutes. For a fudgier brownie, take the brownies out when they are just set and firm at the edges. If you like a firmer brownie, you can cook until the center looks set. If using flake salt, sprinkle the brownies immediately after taking them out of the oven. Let the brownies cool completely before removing them from the pan and slicing. Brownies can be made 1-2 days ahead of time and last for up to a week; they can also be made and frozen for up to two months.