Parsnips are the unsung heroes of the root vegetable world. They are why the mashed potatoes at your favorite 5 star restaurant are so much better than the ones you make at home. They are responsible for the richness in stews, and why your grandmothers squash recipe is so flavorful. Parsnips tend to have a much stronger flavor than a carrot, and that flavor persists better through cooking. Even over long periods like with a large pot roast the parsnips hold their flavor while potatoes and carrots give way to the overall flavor of the dish. Since the flavor is so strong, you do not want to use too many and over power the other vegetables in this recipe. If you are not familiar with parsnips, I suggest tasting a round after they are cooked so you can see what I mean.
We are using equal parts of carrots, potato, parsnips, and onions. Even still the flavor of the parsnips shine through the puree and add a delightful sweetness as a finishing note. This puree really reminds me of something that would be served with a short rib in a fine dining establishment. In fact, as a teenager I worked for a high end dining establishment and the trick to their amazing mash was always the incorporation of another root vegetable.