Heat oven to 400F. While oven preheats, slice Brussels sprouts in half and toss in olive oil.

Roast Brussels sprouts for 30-40 minutes, until soft but still with a "bite".

While the sprouts are roasting, make butterscotch.

In a small saucepan over medium high heat, melt butter and whisk in brown sugar. Stir until sugar melts. Add mustard and whisk for 3-4 minutes until it comes to a light simmer. Season with salt, pepper, and nutmeg. Keep warm until ready to serve.

To serve: spread sauce on the bottom of serving dish and pile up roasted Brussels sprouts. Sprinkle with pistachios.