Preheat the oven to 325°F (163°C).
Set up a double boiler on the stove. Place a heat-tempered bowl over a pan with simmering water.
Add the 10 ounces of chocolate to the bowl and melt it, stirring occasionally until smooth.
In a separate bowl, cream together the 4 whole eggs, 1 cup white sugar, and 1 1/2 teaspoons vanilla extract until creamy and well combined.
Add a splash of coffee (about 1/4 cup) and 1 teaspoon of baking powder to the egg mixture. Mix well.
Gradually add 1 cup of pastry flour or cake flour to the mixture, mixing slowly to avoid clumps.
Pour the melted chocolate and 1 1/2 sticks of melted butter into the batter. Mix until well combined.
Fold in 1 cup of walnuts (optional) or any other desired add-ins, such as chocolate chips or almonds.
Grease an 8x12-inch baking pan with olive oil and line it with parchment paper.
Pour the batter into the prepared pan and spread it evenly.
Place the pan in the preheated oven and bake for approximately 25 minutes.
After 25 minutes, check the brownies by inserting a toothpick into the center. If it comes out with a few moist crumbs, the brownies are done.
Remove the pan from the oven and let the brownies cool in the pan for a few minutes.
Use the parchment paper to lift the brownies out of the pan and transfer them to a wire rack to cool completely.
Once cooled, cut the brownies into squares and serve.