For the vinaigrette: combine all the ingredients and reserve.
For the pears: heat a frying pan with the butter, add the pear wedges and brown on both sides. Sprinkle with sugar and cook for a few more minutes until they caramelized.
Assembling: cover the bottom of a serving plate with the arugula, the caramelized pears on top, then cubes of blue cheese, and finally the walnuts. Drizzle with the vinaigrette and serve.