Sweet Scottish Tablet

Grease and line a baking sheet with parchment paper.

Combine sugar and milk in a large stainless steel pan; stir well. Add sweetened condensed milk and butter; bring to a boil. Reduce heat to medium-low and simmer, stirring often, until mixture turns a deep tan color and is thickened, about 10 minutes. Heat to 240 degrees F (115 degrees C) or until a small amount of mixture dropped into cold water forms a soft ball that flattens when removed from the water and placed on a flat surface.

Vigorously stir mixture, scraping sides down and mixing well. Pour mixture onto prepared baking sheet. Allow to cool at room temperature until set, 1 to 3 hours. Cut into small squares or "tablets".