Grease a 9x13-inch pan, line it with parchment paper, and lightly grease the parchment.

Combine the sugar, whole milk, and butter in a large microwave-safe bowl.

Microwave in 30-second intervals, stirring after each one, until the butter melts and the sugar begins to dissolve.

Transfer the mixture to a large, deep saucepan or stockpot.

Bring to a boil over medium-high heat, stirring occasionally.

Once the sugar has dissolved, carefully stir in the sweetened condensed milk and reduce the heat to medium.

Reduce to a gentle simmer and cook for 15–20 minutes, stirring frequently, until the mixture becomes caramel-gold and reaches 240–248°F.

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

Beat the mixture with a sturdy electric mixer for 8–10 minutes, until it thickens and the mixer leaves trails that do not immediately disappear.

Immediately pour the mixture into the prepared pan. Gently tap the pan to help it settle without smoothing the surface excessively.

Let the tablet stand for about 10 minutes, then score it into small pieces with a lightly greased knife.

Leave it undisturbed for at least 4 hours, or overnight, until completely firm.

Cut along the scored lines and store in an airtight container.