Foolproof Dark Chocolate Condensed Milk Hot Fudge Sauce

Instructions:

1. Place the cubed butter in a medium heavy-bottomed saucepan over medium-low heat. Melt gently until just liquid, taking care not to let it brown.
2. Whisk in the cocoa powder until smooth and lump-free, forming a thick paste. Cook this paste for about 30 seconds, stirring constantly, to bloom the cocoa flavour.
3. Slowly pour in the entire can of sweetened condensed milk while continuously whisking the mixture until fully combined and smooth.
4. Increase the heat slightly to medium, maintaining a gentle simmer. Stir frequently until the sauce begins to thicken noticeably. Simmer for 4-5 minutes.
5. Remove the saucepan from the heat. Immediately add the chopped dark chocolate and the pinch of salt. Let it sit undisturbed for 1 minute to allow the residual heat to melt the chocolate thoroughly.
6. Whisk everything together vigorously until the sauce is completely smooth, glossy, and all chocolate pieces have dissolved.
7. Stir in the vanilla extract.
8. Transfer the hot fudge sauce to a clean, heatproof jar. The sauce will thicken considerably as it cools. Serve warm or at room temperature.