For the honey vinaigrette: In a small Mason jar or any small jar with a tightly fitting lid, combine the mustard, vinegar, honey, and salt and pepper to taste. Cover the jar and shake it to mix the ingredients up a bit. Add the oil and shake for about 30 seconds to mix it all together.
For the fig salad: Preheat the oven to 425 degrees F. Lay the figs out on a baking sheet, cut side up, and drizzle with the melted butter.
In a small bowl, combine the sugar and cinnamon and sprinkle the mixture over the figs. Roast in the oven until the figs are plump and juicy and just slightly softened, about 10 minutes. Allow them to cool to room temperature.
Meanwhile, place the pistachios, thyme leaves, salt and pepper in a small skillet and set over medium heat. Cook, shaking the pan frequently, until the pistachios are lightly toasted and fragrant, 3 to 4 minutes. Transfer the pistachios to a plate to cool.
When ready to serve, scatter the arugula and lettuce on a long board or a platter and drizzle some of your vinaigrette over the greens (the greens should be lightly dressed, not drenched). Place the roasted figs, cut side up, all over the top of the greens. Add little chunks of goat cheese all around the figs, nestle thin slices of prosciutto around the figs and finally, sprinkle over the toasted pistachios. Serve the remaining dressing on the side.
You can use rehydrated dried figs or pears in place of fresh figs.