Cream the butter and sugar together until light and fluffy.
Add the flour and beat until dough-like clumps start to form.
Tip the mixture out onto a floured work surface and use your hands to gently knead it together into a smooth ball of dough - this shouldn't take long, only 30 seconds or less.
Use a large rolling pin to roll the dough out to ¼ inch thick, use cookie cutters to cut out shapes, and transfer them to the prepared cookie sheet.
Chill the cut-out cookies for 1 hour. This is to help them keep their shape in the oven. If you aren't worried about a little spreading, then you can skip this step and put them straight in the oven.
When the chill time is almost up, preheat the oven to 325°F / 160°C.
Bake the cookies for 13-16 minutes, bake time will vary according to thickness, so it's best to look for visual cues when they are ready. As soon as the very edge of any of the cookies starts to turn golden brown, remove them from the oven. They should still look very pale in the middle.
Leave the cookies on the pan for 5 minutes, then transfer to a wire rack to cool.
Decorate with icing of choice - see notes for icing recipe ideas.
Notes
To Decorate:Super Simple Icing - For the easiest, simplest icing, mix 2 cups of powdered sugar in a medium bowl with 2 tablespoons of water and 1 teaspoon vanilla extract or vanilla bean paste. This makes a sweet and simple icing that will be dry to the touch but won't set hard like royal icing would. You can also add a few drops of food coloring to it. Royal Icing - If you want your icing to set hard so you can stack your cookies, or you'd like to decorate your cookies with intricate designs, I recommend royal icing. Do this by beating together 2 egg whites with 2 cups of powdered sugar. Add a splash of water if you'd like a more runny consistency. Chocolate - You can't go wrong with chocolate, especially not when it comes to Valentine's Day! You can drizzle your heart cookies with chocolate or dip them in. You could also pour the melted chocolate over them while they are on the cooling rack. I especially like this with dark chocolate, but you can use any kind you like. Sprinkles - You can't go wrong with sprinkles! You can put sprinkles on top of any of the options above, or even just bake them into the top of the cookie.