Traditional Scottish Butter Fudge

Preheat your oven to 350 degrees F (175 degrees C) and line a 13x18-inch baking sheet or two 8x8-inch square pans with parchment paper, setting them aside for now.

In a large saucepan, combine sweetened condensed milk, heavy cream, granulated sugar, salt, and unsalted butter. Place the saucepan over medium heat and bring the mixture to a rolling boil, stirring constantly to prevent scorching. As the mixture reaches its boiling point, reduce the heat to low and continue cooking and stirring until it reaches a temperature of 234-240 degrees F (112-116 degrees C) on a candy thermometer, or until a small amount of the mixture forms a soft ball that flattens when removed from cold water and placed on a flat surface. This process should take approximately 20 minutes.

Once the mixture has darkened in color, remove it from the heat source and vigorously beat it with a wooden spoon until it cools and thickens. Stop beating once the mixture becomes grainy to the touch, as this indicates it has reached its desired consistency. Stir in a few drops of vanilla extract.

Pour the mixture into the prepared pans and let them cool to room temperature. Resist the temptation to scrape any crystallized bits from the bottom of the pans, as this can cause the entire batch to become crystalline. Allow the mixture to set for 6 hours or overnight, depending on your schedule.

Once the mixture has hardened, use a serrated knife to cut it into 2-inch squares. Store the finished tablets in an airtight container at room temperature, away from direct sunlight.