Line an 8-inch square baking pan with aluminum foil, leaving enough overhang on the sides to easily remove the caramel once it has set. Lightly grease the foil with butter.

Combine the cream, granulated sugar, brown sugar, and corn syrup in a 3-quart heavy duty saucepan over medium heat. Using a wooden spoon, stir constantly as the sugars dissolve. The mixture will be thick and cloudy looking.

Once boiling, brush down the sides of the pan with a water-moistened pastry brush. Attach a candy thermometer to the pan, making sure not to let it touch the bottom.

Without stirring, cook until the temperature reaches 245°F (118°C). Immediately remove from heat and stir in 1 teaspoon of salt, the vanilla extract, vanilla bean seeds, and butter. The mixture may burst and bubble, so be careful stirring.

Pour the hot caramel into the prepared baking pan and top with coarse sea salt, if desired. Allow to cool at room temperature, uncovered, for 4 hours or overnight (no need to cover).

Once set, remove the caramel from the pan by lifting out the aluminum foil. Peel the foil off and, using a very sharp knife, cut into rectangles or squares. Wrap with candy wrappers, if desired.