Line a half sheet pan with a nonstick rubber mat. Place a 38cm / 15in by 25cm / 10in wide by 2cm / 0.75in Plexiglas frame on the mat and freeze.
Pour the soufflé base into the prepared pan and even out the top with an offset spatula so that it is flush with the frame. Place in the freezer until hardened.
Once hardened, take the frame off the soufflé (run a paring knife along the inside border, being careful to not cut the rubber mat). Flip the soufflé over onto an acetate sheet of the same size as the soufflé and peel the rubber mat off.
Cut into rectangles 1.25cm / .5 in by 12.5cm / 5 in. Return to the freezer.
Set up the spraying area. Place the chocolate spray in a spray gun and spray the soufflés until they are completely coated.