Preheat oven to 350℉. Peel and trim ends from parsnips, cut into 1" chunks. Boil or steam until tender, about 10 minutes depending on size. Drain well and mash with a fork or potato masher until all large chunks are broken down. The parsnips will remain stringy with small bits still visible. While parsnips are cooking, grate a cleaned piece of raw pumpkin flesh using a fine grater. Add grated pumpkin to mashed parsnips along butter, brown sugar, nutmeg, cinnamon and salt. Stir to combine. Spread evenly into a small buttered casserole dish (makes about 3 cups). Sprinkle topping evenly over casserole and bake in preheated oven for 20-25 minutes until golden and starting to bubble in the center. Remove and allow to rest for 2-3 minutes.