Preheat oven to 350 degrees F. Line two half sheet baking pans with silicone baking mats (parchment paper will work, but I find silicone to be easier to spread on and it bakes more evenly as well).
Cream butter with powdered sugar until smooth. You can use an electric mixer if you'd like, or do it by hand with a spoon or spatula.
Add egg and beat or use a whisk until incorporated and mostly emulsified.
Sift flour, salt, and baking soda. Add molasses, then mix until smooth and no streaks or chunks of dry flour remains.
Drop ¼ of batter (about 50-60g worth or a large cookie scoop) onto prepared baking pan. Use an offset spatula to spread batter into a very thin, even layer over the entire surface.
Bake for 4 to 6 minutes, rotating baking pan halfway through, and keeping a close eye on it during the last couple minutes especially as it will burn rather quickly.
Remove from oven and let cool on baking sheet for 10 to 15 minutes; it will crisp up as it cools. Once cool, break into pieces and pour into a bowl or storage container.
Repeat with remaining batter on cooled sheet pans.
