Place one cup of McEwan's Balsamic Vinegar along with brown sugar in a heavy-bottom saucepan over low heat. Simmer, stirring frequently, until vinegar is thickened or the back of a spoon is coated. Remove from heat and allow to cool. Sauce will thicken as it cools.
To assemble crostini
Cut baguette into one-third inch slices, on a bias. Lightly coat with olive oil and bake for eight minutes until lightly toasted. Slice brie into thin strips and place on bread. Top with prosciutto and a generous teaspoon of Cranberry sauce. Sprinkle chopped walnuts, if using, and drizzle balsamic glaze over assembled crostini. Embellish with mint leaves or arugula.