Meanwhile, melt butter in a large skillet over medium heat. Once melted, add the snap peas, asparagus, broccolini, and shallots, and gently cook for 5-8 minutes, stirring occasionally, until the vegetables are tender-crisp (reduce the heat as necessary if you start to see that the butter is turning brown). Using tongs or a slotted spoon, remove the veggies, and place on serving plates.