Rum Sauce for Plum Pudding

This rum sauce accompanies the plum pudding brought from Scotland by my great grandmother Nana Ross.

Ingredients
2 cups boiling water
1/2 cup brown sugar packed
2 tablespoons butter
1/8 teaspoon salt
1 to 2 tablespoons round table cornstarch
1 teaspoon vanilla
unlimited supply of rum

Procedure
Add sugar, butter and salt to water
Add cornstarch to thicken.
Take off heat.
Add rum to taste.
Add vanilla.