Lay out a large piece of parchment paper. This should be large enough to fit a 10 x 16" rectangle with room around each side.
In a heavy duty, thick bottomed pot, combine all caramel ingredients except for chocolate.
Cook over medium - low, stirring constantly, until butter has melted and sugar is dissolved.
Turn heat to medium. Stirring constantly, bring mixture to a boil.
Turn heat to medium high. Cook caramel until temperature reaches 244F.
Turn off heat. Add in chocolate. Stir until combined.
Pour caramel on parchment. Spread into a thin layer, making a 10" x 16" rectangle. Cool completely. Make cream center while it cools.