Grease a 8x8 pan with cooking spray. I used a pan with 12 small hearts.
In a large saucepan, add in the butter, brown sugar, corn syrup, and sweetened condensed milk. Place it over medium heat and stir the ingredients with a spatula.
Once the mixture comes up to a boil, place a candy thermometer on the side of the pan. Continue stirring so the mixture doesn't burn.
Once the caramel comes up to 250 degrees, turn off the heat and spoon the caramel into the pan. Let the caramel cool.
In a microwave safe bowl, place the chocolate and shortening. Microwave for 30 second intervals until the chocolate and shortening is melted. Stir after each interval. It took a minute for mine.
Dip the cooled caramels into the chocolate and tap off the extra chocolate. Place on a piece of parchment paper to dry and add some decorative sprinkles.
They can stick together if they're not covered in chocolate, so be careful not to layer them.