This is a mixture of goat cheese, Gorgonzola, and walnuts inside a wheel of Brie, sliced into two disks. Before serving, spoon red grapes in port syrup over the cake.
In the bowl of an electric mixer fitted with the paddle attachment, beat goat cheese and blue cheese until mixture is softened and smooth.
Using a sharp serrated knife, carefully slice Brie in half horizontally, gently easing the two halves apart. Spread 3/4 cup goat-cheese mixture on one half; sprinkle with walnuts. Place other Brie half, cut side down, on top of walnuts.
Using an offset spatula, spread remaining goat-cheese mixture over top half of Brie. Chill two hours or overnight.
Up to one hour before serving, combine port, honey, and two sprigs thyme in a medium saucepan. Bring to a boil over medium-high heat, cook until reduced by half, about six minutes. Add grapes; cook 30 seconds more. Using a slotted spoon, transfer grapes to a bowl; let cool. Reduce remaining liquid until thickened, about six minutes. Remove from heat.
Just before serving, place cake on a platter, and arrange grapes on top of goat-cheese mixture. Drizzle with port syrup. Garnish the platter with walnut halves and thyme sprigs.
This cake is delicious at room temperature. If making it the night before, remove cake from refrigerator at least two hours before serving.