Using a paring knife, trim away any mold from the goat cheese and coarsely chop. Shred the Gruyere cheese. Place the wine and garlic in a small, heavy saucepan. Bring to a boil over low heat and allow to reduce by half. Add the goat cheese and let melt over low heat, stirring with a wooden spoon. Remove the garlic. Add the Gruyere and butter and stir over low heat until the cheese are melted and well blended. Remove from the heat and stir in the mustard and Marc. Preheat the broiler. A few minutes before serving, place the bread slices on a baking sheet and toast. Remove from the oven and immediately spread each slice with warm fondue. Garnish with a sprig of fresh savory or thyme and top with a grind of fresh pepper.
Recipe courtesy Roger Verge, from Roger Verge's Entertaining in the French Style, published by Stewart, Tabori and Chang, 1986