Step 1

Line 8-inch square (2-quart) glass baking dish with waxed paper or cooking parchment paper.

Step 2

In 2-quart saucepan, heat 2 1/2 cups butterscotch chips and 1 can (14 oz) sweetened condensed milk (not evaporated) over medium heat, stirring occasionally, until melted.

Step 3

Remove from heat; stir in 1 teaspoon vanilla and 1/2 teaspoon kosher salt. Spread in baking dish; refrigerate about 4 hours or overnight. Cut into 8 rows by 8 rows for 64 (1-inch) squares.