Preheat the oven to 175C (350F) and line 2 baking sheets with parchment paper.
In a bowl, combine the flour, baking soda, and salt.
In the bowl of a stand mixer (or a mixing bowl with a hand mixer or whisk), add the butter, granulated sugar, brown sugar, and vanilla extract. Beat on medium for 1-2 minutes until the mixture resembles a smooth, homogenous paste, scraping down the sides and bottom of the bowl as needed.
Add the molasses and beat until fully incorporated.
Add the egg and beat until the mixture is fully emulsified and smooth.
Gradually add the dry ingredients, mixing on low speed just until no dry streaks remain.
Scoop out 14 balls of cookie dough, approximately 35 g each, and place them on a baking sheet, leaving 2 inches (5 cm) of space between each.
Bake in two batches for 12-13 minutes, or until the cookies have spread and the edges are golden.
Remove from the oven and gently tap the baking sheet on a flat surface to deflate the cookies. Let them cool on the baking sheet for 10 minutes, then transfer them to a cooling rack to cool completely.