Combine 1 can of coconut milk, brown sugar and salt in a medium sauce pan. Set over medium-high heat and bring to a boil, stirring occasionally so that the sugar dissolves. Once boiling, reduce he heat slightly and continue to cook until the mixture has darkened and reduced, about 20-30 minutes. It should be very thick - like lava - resembling caramel.

While the caramel is reducing, beat the egg yolks in a large heatproof bowl and set aside.

Add the second can of coconut mile to the coconut caramel and heat, stirring to integrate the caramel. When the mixture is very hot, but not boiling, temper the egg yolks: slowly whisk 1 cup of the caramel mixture into the bowl with the egg yolks.

Turn the heat to low and pour the tempered yolks back into the pot. Cook, stirring constantly, just until the mixture has thickened, 1-2 minutes. Remove from the heat and pour into a heatproof bowl. Stir in the vanilla extract. Cover tightly and refrigerate overnight.

Pour the custard mixture into an ice cream maker and churn according to manufacturer's directions. Freeze for 4-6 hours before scooping and serving.