Preheat the oven to 350 degrees F. Put the butter in an 8 by 8-inch baking dish and put the dish in the oven until butter is melted, about 3 to 4 minutes. Remove the baking dish from the oven and set aside. In a medium bowl combine 3/4 cup of the sugar, the flour, and 2 tablespoons cocoa. Add the milk and vanilla, whisking until smooth. Pour over the melted butter in the baking dish. In a separate medium bowl, combine the remaining 1 cup of sugar, remaining 4 tablespoons of cocoa, the pecans, and toffee bits; sprinkle evenly over the sugar mixture. Slowly pour boiling water over top of the cobbler. Bake until top of the cobbler looks set, about 40 to 50 minutes. Serve warm with Caramel Whipped Cream, ice cream and pecans, if desired.
To make the Caramel Whipped Cream: Combine the cream and sugar in a medium bowl and beat with a whisk or beater until soft peaks form. Add the caramel syrup, and lightly fold together.