Make the dressing. In a small bowl, whisk together the lemon juice and Dijon. Gradually add the olive oil, whisking continuously until the mixture is emulsified. Season with salt and pepper.
Toss. In a large bowl, toss together the arugula and shallots. Add the dressing and toss well to coat. (You probably don't need to use all of the dressing)
Arrange the board. Spread the arugula on a large board and arrange the prosciutto and figs on top of it. Finish with a sprinkling of blue cheese. Serve immediately.