To make the fig jam: Add all of the ingredients to a small saucepan. Bring to a boil over medium to high heat and then turn down to simmer for 12 to 15 minutes. Turn off the heat, allow mixture to cool slightly, remove the rosemary sprig, and then puree using an immersion blender.
To make the crostini: Preheat oven to 400 degrees.
Cut the baguette on the bias into 8 slices. Place on a sheet tray and drizzle with oil and sprinkle with salt and pepper. Toast in the oven for 15 minutes.
Remove bread from the oven and allow to cool. Top each slice with 1 tablespoon fig jam, and then sprinkle with blue cheese and walnuts.