Add the butter and sugar to a large mixing bowl and beat until light and creamy.
When the butter is creamy, add the flour and beat on a low speed until a dough is formed (about 30 seconds).
Place the dough between two sheets of wax or parchment paper and roll out to about 1/4 inch thick. Chill dough at least 30 minutes (or up to overnight).
Preheat oven to 350°F and line cookie sheets with parchment paper or silicone baking mats.
Take the dough from the refrigerator and remove the sheets of wax paper.
Using a cookie cutter, cut the dough into 24 hearts. Re-rolling the dough as many times as needed to use it all up, chilling it before cutting and baking.
Transfer the cookies onto the baking sheets, leaving a small amount of space in-between.
These cookies will not spread or lose their shape during baking.
Bake for 10-15 minutes, or until they lose their glossy sheen and are just light golden around the edges. Once baked, the cookies will still be soft so leave them to cool for 10 minutes on the baking sheets before transferring them to a cooling rack.
When the cookies are cool, melt the chocolate in a microwave-safe bowl on 50% power, stirring every 30 seconds until melted and smooth. Dip the cookies in, coating half of the cookie with chocolate. Add the sprinkles. Place on baking parchment to set.