You absolutely can! Buying a canned puree just makes things easier but if you have the time making your own puree is even better because of the fresher taste. Don't use the large, ornamental pumpkins used for jack o' lanterns. Instead buy smaller pumpkins that are sold as "pie pumpkins" or use other winter squash, including butternut squash and acorn squash. Peel the squash, cut into 1-inch cubes, toss with oil, and roast in a 400 degree oven for 40 minutes or until very tender. Blend into a puree.