Yield: Twenty 7.5-cm x 7.5-cm (3-in x 3-in) brownies
300 (10.58 oz) grams unsweetened chocolate
450 (15.87 oz) grams unsalted butter
450 (15.87 oz) grams whole eggs
900 (31.74 oz) grams superfine (caster) sugar
15 (00.53 oz) grams pure vanilla extract
300 (10.58 oz) grams all-purpose flour, sifted
ProcedurePreheat oven to 180°C (350°F). Line one half-size sheet pan (46-cm x 33-cm x 2.5-cm / 18-in x 13-in x 1-in) with non-stick baking paper. Allow the paper to extend 2.5-cm (1-in) on each short side of the sheet pan. This will make removing the slab of brownies after cooling easier.
Melt together unsweetened chocolate and unsalted butter in a double boiler. Remove from heat and maintain temperature of chocolate / butter mixture at 30°C (86°F).
Meanwhile, combine whole eggs and superfine (caster) sugar in a 4.75-liter (5-quart) mixer bowl. Using the paddle attachment, beat on low speed (Speed 2 on a Kitchen Aid mixer / Speed 1 on a Hobart mixer) for 1 minute. Stop mixer and scrape down bowl.
Add chocolate / butter mixture. Beat on low speed for 1 minute. Stop mixer and scrape down bowl. Stir in pure vanilla extract.
Add sifted flour. Beat on low speed 1 minute. Stop mixer and scrape down bowl.
Deposit the batter into prepared sheet pan. Bake in preheated oven 40 minutes. A wooden pick inserted in the center will come out with moist crumbs.
Cool to room temperature. Double-wrap slab of brownies in sheet pan with cling wrap and refrigerate at least 4 hours or overnight.
To unmold, loosen the slab of brownies from the sheet pan using a small sharp paring knife. Lift out the slab of brownies using the overhang of non-stick baking paper.
Using a long sharp chef's knife, trim off 1.25-cm (1/2-in) from each long side of the slab. Trim off 3.75-cm (1-1/2-in) from each short side of the slab. Cut the slab into twenty 7.5-cm x 7.5-cm (3-in x 3-in) brownies.