1. Preheat oven to 325 degrees. Cut baguette into sixteen 1/4-inch-thick slices and three 1/2-inch-thick slices. Cut 1/2-inch-thick slices into cubes; soak in broth. Arrange slices on a baking sheet. Brush one side with oil. Toast in oven about 10 minutes. Using a mortar and pestle, pound and stir garlic, salt, saffron, and cayenne into a paste. Squeeze broth from cubes (reserve broth); add cubes to mortar. Add yolk; pound and stir. While stirring, add oil in a slow, steady stream until emulsified. If needed, thin with reserved broth. Serve on croutons.