Nota bene: This recipe needs constant attention, moves quickly, and involves extremely hot sugar that requires careful handling, so it’s necessary to have everything prepared in advance.
Grease a half-sheet pan (460 mm x 330 mm, 18” x 13”).
Grease the tines of a pair of forks and set aside.
Prepare a heatproof surface or put trivets or hot pads in place on which to set the half-sheet pan in such a way that it will not shift or tip.
Set out a silicone spatula and table knife.
Measure the remaining ingredients.
Place the sugar and the 57 g butter in a 10- or 12-inch skillet. Place the skillet over high heat. As the sugar melts around the edges, begin stirring the sugar and butter. Stir constantly as the sugar melts. It will form clumps before melting; if necessary, use the table knife to knock any clumps off your stirring utensil and back into the pan.
The sugar will caramelize, changing to a light brown syrup. This will take about ten minutes. The moment the last grains of sugar disappear, turn off the heat.
Add the salt. Protecting your hand and standing at a safe distance to avoid syrup spattering, add the vanilla and almond extracts. The extracts will crackle violently. Swiftly pour in the crushed almonds. Turn the heat back on, and set it to medium.
The almonds will bring the heat of the mixture down, and it’s necessary to bring it back up before forming the brittle. Begin stirring the crushed almonds and the syrup together.
When the almonds and syrup are completely incorporated, increase the heat to medium high and cook, stirring, until the mixture is quite fluid.
When the mixture is fluid, turn off the heat.
Pour the mixture onto the half-sheet pan. Working quickly, take the forks in hand, and spread and pull the mixture to cover as much of the half-sheet pan as possible.
When the mixture is spread, sprinkle the chocolate chips over it evenly. Let the chips stand a few minutes to soften. When they've melted sufficiently, use the offset spatula to spread them over the surface of the brittle.
Allow the brittle to cool to room temperature, which will take a couple hours. When it has cooled, break it into pieces by hand.