Eggnog Caramel Brownies

Make the eggnog caramel: In a small saucepan, heat the sugar and water over medium-high heat, swirling it often to dissolve the sugar, until the sugar melts and turns into a fully liquid golden-brown caramel. Remove the pan from the heat and whisk in the butter until it emulsifies with the sugar and is smooth. Pour in the cream and whisk until smooth. Stir in the nutmeg, cloves and salt, followed by the rum and vanilla. Transfer the caramel sauce to a bowl and let stand until cool to the touch. Whisk in the egg yolks, then refrigerate the caramel sauce until cold and thickened, at least 1 hour. You can prepare this caramel sauce up to three days ahead of time.