In a thick-bottomed pot, combine the unsalted butter, brown sugar, salt, evaporated milk, heavy cream, and corn syrup. Cook over medium-low heat, stirring continuously until butter melts and sugar dissolves. Increase heat and bring to a gentle boil, about 5 minutes.

Raise heat to medium-high and continue to cook, stirring constantly, until temperature reaches 241°F or the soft ball stage (about 10-15 minutes).

Carefully pour caramel onto a prepared baking tray lined with parchment paper and spread into a uniform rectangle. Allow to cool completely for about 30 minutes.

While caramel cools, prepare vanilla cream filling by mixing vegetable shortening and powdered sugar until fluffy. Gradually add vanilla extract and corn syrup, incorporating water one tablespoon at a time until thick and spreadable.

Cut cooled caramel slab into four equal pieces. Spread vanilla cream filling on each piece, leaving a ½-inch border. Roll each piece tightly into logs.

Cut logs into ½-inch slices with a warm knife for neat cuts. Wrap each slice in cello wrap or parchment paper.