Line a 9x9 inch baking pan with parchment paper and rub it with butter.

In a large, heavy saucepan, melt the butter over medium heat.

Add dark brown sugar and stir until incorporated.

Stir in the light corn syrup and let it simmer gently.

Cook over medium-low heat for about 3 minutes, stirring occasionally until sugar is dissolved.

Stir in the sweetened condensed milk and bring the temperature to medium, stirring constantly.

Cook until mixture reaches 238° to 240° on a candy thermometer (20-30 minutes).

Remove from heat and stir in the vanilla extract.

Pour into the prepared pan and let cool to room temperature for 3-4 hours.

Once set, lift the caramel block from the pan using the parchment paper and cut into desired sizes.

Wrap each caramel in waxed paper.