Macadamia Shortbread Brownies
Adapted from Bittersweet
Makes 25 brownies

For the crust:
6 tbsp. unsalted butter, melted
2 tbsp. sugar
¼ tsp. vanilla extract
Pinch of salt
¾ cup all purpose flour
½ cup untoasted unsalted macadamia nuts, chopped medium-fine

For the brownie batter:
6½ ounces bittersweet chocolate, chopped
7 tbsp. unsalted butter, cut into 7 pieces
1 cup sugar
1 tsp. pure vanilla extract
¼ tsp. salt
2 large eggs
½ cup all purpose flour

Make the crust:
Position a rack in the lower third of the oven and preheat to 350ºF.  Line a 9-inch square baking pan with foil and make sure the ends extend up over the sides by several inches.  (This will serve as handles to remove the brownies from the pan once they are baked.)

Combine the melted butter, sugar, vanilla, and salt in a bowl.  Stir in the flour to make a dough.  Scrape the dough into the prepared pan and, using your fingers, press the dough all over the bottom of the pan and just a bit up the sides.  Bake until the crust is nicely brown all over, 15 to 20 minutes.

Make the brownie batter:
Combine the chocolate, butter, and sugar in a medium heatproof bowl.  Place the bowl over a pot of simmering water.  Stir frequently until the chocolate is melted and the mixture is smooth and hot enough that you want to remove your finger fairly quickly after dipping it in to test.

Remove the bowl from the pot.  Stir in the vanilla and salt with a wooden spoon.  Add the eggs, one at at time, stirring until the fist one is incorporated before adding the next.  Stir int he flour and beat with a wooden spoon or rubber spatula until the batter is smooth, glossy, and beginning to come away from the sides of the bowl, 1 to 2 minutes.

Assemble the brownies:
Spread the brownie batter evenly over the hot crust and bake until the edges puff and begin to show fine cracks, 20 to 25 minutes.  Let cool completely in the pan on a rack.

Remove the brownies from the pan by lifting up the ends of the foil, and transfer to a cutting board.  Cut into 25 squares with a heavy knife.