Prepare all the ingredients and treats for dipping.

In a small bowl, combine the chocolate, 1/2 cup milk, and butter (if using) and melt gently in a barely simmering water bath or microwave on medium power for about 2 minutes.

Stir until completely smooth. Add more milk if desired.

Remove from heat and stir in the vanilla and salt.

Serve the warm fondue immediately with chosen dippers.

If the fondue gets too thick or starts to harden, reheat in the microwave in bursts of 15 seconds, stirring between each burst for 10 seconds until melted and smooth again.