Rhubarb and rosemary are surprising bedfellows in this creme brulee. The result was subtle but notable, producing a creme brulee that is at once rich and creamy, sweet and tart, earthy and heavenly. Remove from the heat, discard the rosemary sprig, and cool to room temperature. Spoon some of the rhubarb compote into the ramekins, about 1/3 inch deep. Let the cream steep for 5 minutes, then discard rosemary sprig.