Grease a 9x9-inch baking pan and line it with parchment, leaving an overhang for easy removal.

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

Add the brown sugar, corn syrup, and salt; stir until the sugar is moistened and the mixture is smooth.

Gradually pour in the sweetened condensed milk, stirring constantly to combine.

Bring the mixture to a gentle boil, continuing to stir. Cook for about 15–20 minutes until it reaches 245°F (soft-ball stage) on a candy thermometer. If you don’t have a thermometer, test by dropping a small spoonful into very cold water: it should form a soft, pliable ball.

Remove the pan from heat and stir in the vanilla extract.

Pour the caramel into the prepared pan and smooth the top.

Let cool completely at room temperature, at least 2 hours, then lift out via the parchment and cut into squares.

Wrap each piece in wax paper for storage or gifting.