In a mixing bowl or the bowl of a stand mixer, add softened butter and soft brown sugar.
Using an electric beater or the paddle attachment, beat the butter and sugar until smooth and creamy - about 1-2 minutes.
Then, sift in the flour and beat on low-speed - speed 2-3 of a stand mixer - until fully incorporated.
If too dry or crumbly - add 1-2 teaspoons of milk or water. If too wet, add 1-2 tablespoons of extra flour. The texture should be soft and creamy but not overly sticky.
Transfer the creamy cookie dough to a plastic wrap, flatten it into a disc, and refrigerate for 1-2 hours.
After the chilling time, preheat oven to 350°F (180°C). Line a baking sheet with parchment paper. Slightly oil paper with cooking oil spray, Set aside.
Flour a work surface, remove the disc of dough from the fridge, unwrap it, add some flour on top, and knead for a few seconds.
Place the dough on the floured surface, then sprinkle extra flour on top.
Use a rolling pin to roll the dough to a 1/4-inch thickness, then cut it out into any shape you like.
Gently side a spatula under each rolled cookie to transfer them to the baking sheet. Be gentle! The dough is soft and fragile. You can also roll and cut out the dough directly on a piece of parchment paper. Then slide the parchment paper onto a baking sheet.
Leave a thumb space between each - they won't expand, but it's easier to remove them from the tray later.
Bake for 8-12 minutes until just crispy on the edge and golden brown.
Cool down on the baking sheet for 5 minutes, then transfer to a wire rack.
Cool completely before decorating.