Line a 9x9 inch square pan with two pieces of parchment paper, creating a sling for easy removal.

In a medium bowl, cream the butter until smooth, then add the powdered sugar and beat for 2 more minutes.

Mix in the flour, salt, and vanilla until just combined.

Add the dough to the prepared pan and press it into an even layer with plastic wrap. Chill in the fridge for at least 30 minutes.

While the base is chilling, preheat the oven to 325 degrees F.

Dock the dough with the tines of a fork. Bake the shortbread for about 30 minutes or until the edges are lightly golden brown. Allow to cool completely before pouring the caramel on top.

Brown the butter: In a small saucepan, add the butter and place over medium heat. As the butter melts, stir it with a rubber spatula to encourage even cooking. Once the butter has fully melted, it will alternate between rapid large bubbles and gentle small foamy bubbles. The butter will be ready once it turns a dark golden color and the fat solids have darkened and settled at the bottom of the pan.

To the brown butter, add the brown sugar, sweetened condensed milk, and light corn syrup. Heat over medium heat, whisking frequently until it reaches 235 degrees F.

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

Pour the caramel over the cooled shortbread base and quickly spread into an even layer. Chill the bars in the fridge uncovered for at least two hours or overnight.

Once chilled and set, cut into 30 bars (10x3). Place the bars in the freezer while you melt the chocolate.

In a medium bowl, add the chocolate and oil. Heat in the microwave in 30 second intervals until fully melted.

Working quickly, dip each Twix bar in the chocolate and place on a baking sheet to set.