Preheat your oven to 350F and oil a 10-inch, well-seasoned cast iron skillet (a nonstick skillet will also work well!).

Mix together the flour, coconut sugar, cocoa powder, baking soda, and sea salt in a mixing bowl. Separately, whisk together the tahini, yogurt, and vanilla.

Melt 5 ounces of the chocolate chunks or morselsin the microwave or over a double boiler. Add the tahini/yogurt/vanilla mix to the melted chocolate and combine well. Add this mixture to the dry ingredients. The batter will be very thick. Fold in the remaining 3 ounces chocolate chunks or morsels.

Spread the batter into your skillet. Bake for 22 minutes, or until the top is set and the edges firm. Remove the skillet brownie from the oven and allow it to cool for at least 30 minutes before serving with the frozen mousse.