I always make sure to bake some heart-shaped cookies for Valentine's Day. I often make my "sugared" sugar cookies - which are really just sugar cookies, covered with icing and sprinkled (liberally) with colored sugar.
Here's how I make them: I always start with a a good basic sugar cookie recipe - my favorites are from the incredible Glory of Glorious Treats and Martha Stewart. You will also need icing in as many shades as you wish (I chose light pink, hot pink, lavender, and mint) and matching sugars in the same colors.
People always ask me for my pourable icing recipe, but the truth is, I don't use an actual recipe. I just kind of wing it - in a bowl, I place some sifted (for smooth icing) powdered sugar. Then I add some milk, one tablespoon at a time until the icing is thick, but still pourable. I also like to add some clear vanilla extract for flavor. When I have my desired consistency, I add my food coloring.
As for the colored sugars, you can easily buy them at the supermarket or cake decorating supply shop. But, if you are picky about exact colors and/or want to save some money - tint your own - it's soooo easy. Just place some sugar in a ziploc baggie with a bit of powdered food coloring and shake it up. That's it!
After my cookies are baked and cooled, I place them on a wire rack set inside a larger cookie sheet that has sides (this is a must or you will have icing flowing all over the place). To decorate the cookies, I just pour the icing over the cookies until they are completely covered and then quickly sprinkle on the matching colored sugar. Yes, it's a bit messy, but really simple - and the mess stays in the pan!