Line an 8×8-inch dish with parchment paper or lightly grease it. Set it aside.

In a microwave-safe bowl, combine the butter, corn syrup, brown sugar, granulated sugar, and sweetened condensed milk.

Microwave the mixture for 6 minutes, stopping every 2 minutes to stir thoroughly.

Once the 6 minutes are up, stir in the vanilla extract. To test doneness, drop a small amount into cold water. It should form a soft, pliable ball.

Pour the caramel mixture into the prepared dish, spreading it evenly.

Allow it to cool at room temperature for 1-2 hours, then cut into bite-sized pieces and wrap in wax paper for storage.