Heat treat your flour by microwaving it in a bowl for around 1 -2 minutes or until it's hot, or pouring it on a baking sheet and baking it in a preheated oven (350°F) for 5 minutes (or microwave for 1-2 minutes), then set aside to cool* Heat treat around 2 tablespoons more than the recipe calls for, then measure out the exact quantity after. (SEE NOTES)
In a medium bowl, use a wooden spoon, spatula, or a mixer to mix butter and sugar together. Add in the vanilla extract.
Mix in the heat-treated flour and salt, then add in the milk slowly until a cookie dough consistency is reached. Stir in sprinkles, chocolate chips, or other desired mix-ins.
