First make the caramel in a medium sized pot. Start by adding the butter, brown sugar, corn syrup, and sweetened condensed milk to the pot and bring to a boil. Try not to stir it, just swish it around with the pot handle. Stirring can make the caramel crystallize.
Heat the caramel till it reaches 245 degrees on your candy thermometer, or use the cold water test for the soft ball stage. Take off the heat and cool slightly.
Melt the chocolate over a small pot of simmering water. Put chocolate in a bowl and place over the pot and stir till the chocolate has melted.
Spoon over the caramel. Sprinkle with some sea salt and let the chocolate harden.
Nutrition facts are approximate and depend on how big your turtles are.