In a stand mixer fitted with the paddle attachment, or in a large bowl with a hand mixer, cream the butter and light brown sugar together until light and fluffy. This will take 1-2 minutes.
1 ½ sticks unsalted butter, 1 cup light brown sugar
Add the molasses, egg, vanilla extract and apple cider vinegar. Beat on medium speed for 2 minutes. Make sure to scrape down the sides and bottom of the bowl so all of the batter is combined!
2 teaspoons vanilla extract, 1 large egg, ¼ cup unsulphured molasses, 1 teaspoon apple cider vinegar
Add the dry ingredients to the wet ingredients and mix on your lowest speed. As soon as there are no more streaks of flour, stop the mixer.
Place the cookie dough in the fridge to chill for at least 1 hour. If you want to leave it any longer (you can leave it overnight!) I recommend covering the top of the bowl with plastic wrap.
Preheat the oven to 375°Fahrenheit/190°Celsius and line 2 baking sheets with parchment paper.
Take the cookie dough out of the fridge, it should be quite firm. Scoop out the dough in 1 ½ tablespoon balls. Roll the cookie dough between your palms to form them into perfect cookie dough balls. Roll the cookie dough in the white sugar until completely covered. Repeat with all of the dough.
½ cup white sugar
Place the cookie dough balls on the prepared cookie sheets, making sure they are 3 inches apart.
Bake the cookies one sheet at a time for 10-12 minutes. Keep the remaining unbaked cookie dough balls in the fridge so they don't become too warm. The cookies are done when they have cracked on top and the edges are set. The dough in the cracks might look slightly underdone which is what you want, that way you have a soft and chewy cookie!
If the cookies aren't as cracked as you would like, bang the cookie sheet on your counter or stove once or twice, this will create more cracks. Let the cookies cool on the baking sheet for 15 minutes before moving to a wire cooling rack to cool completely.
Notes
My recipes have been developed and tested in metric grams. I highly recommend using a weighing scale and measuring out your ingredients the metric way. .Butter: I use European style butter, like Kerry Gold, in my recipes. This will make your finished bake much creamier and richer.Salt: If you don’t have kosher salt, halve the amount of salt called for in the recipe. 1 teaspoon kosher salt = ½ teaspoon fine salt. Please note, I am using Diamond Crystal kosher salt and not coarse salt. Molasses: Make sure you are using unsulphured dark molasses. You can also use treacle if you don't have molasses.Storage: keep the baked cookies in a tupperware for up to 1 week at room temperature. Freeze unbaked cookie dough balls for up to 2 months. When ready to bake, take them out of the freezer and bake at the same temperature as above but for an extra minute or two.