Preheat the oven to 325°. Line an 8- or 9-inch square baking pan with foil. Coat the foil with butter.
To make the caramel filling, heat the sugar in a medium saucepan with a heavy bottom, stirring constantly. The sugar will lump and then melt to a deep golden brown. Watch carefully—sugar burns easily. Add the bacon drippings and the butter, if using, and stir vigorously. Remove from the heat and drizzle in the cream carefully (it will steam and bubble), beating rapidly to mix. When the mixture is smooth and the bubbling has calmed, set it aside to cool for at least 15 minutes.
To make the brownies, combine the sugar, cocoa powder, and salt in a mixing bowl. Melt the butter, pour it over the mixture, and stir until well blended. Add the vanilla and eggs, and stir. Then stir in the flour just until blended; the batter will be very thick.
Spread half of the brownie batter in the pan. Top with all but 1 tablespoon of the caramel and spread evenly over the brownie layer. Use a spoon to drop the remaining brownie batter gently onto the caramel. Use an offset spatula or the back of a spoon to gently spread the batter over the caramel.
Bake for 30–35 minutes or until a toothpick inserted is almost clean when removed. Remove from oven. Drizzle the reserved caramel over the brownies. Place the pig candy (see below) gently on top of the brownies and return the pan to the oven for 3–5 minutes to set.
Cool in the pan for 10 minutes. Lift the foil from the pan and place on a cooling rack to cool completely. Cut into small squares.