Caramelize the sugar

• Add the brown sugar to a saucepan over medium heat.
• Let it sit until it melts and caramelizes into a completely smooth caramel.

Add the hot water

• Pour in the hot water; some pieces will harden but will melt back down.
• Stir until everything is melted and smooth again.

Add condensed milk and salt

• Add the sweetened condensed milk and mix until fully combined.
• Stir in the sea salt flakes.

Simmer

• Bring the syrup to a simmer and let it simmer, then remove from the heat.

Cool and strain

• Let the syrup cool in the pan.
• Strain it through a sieve.

Finish and store

• Stir the vanilla extract into the strained syrup.
• Pour into a container and fill it to the top.