The original recipe called for calabaza pumpkin, whose flesh cooks to a golden-yellow color, to be cooked to tenderness in large pieces with the peel left on. For this version, the squash is peeled, cubed and sauteed with a little olive oil. Acorn squash may be substituted. The Washington Post, October 29, 2008 Adapted from a Yucatan recipe in Diana Kennedy's "The Essential Cuisines of Mexico (Clarkson Potter, 2000) Tested by Bonnie S. Benwick for The Washington Post. "MAKE AHEAD: The cooked vegetable mixture can be frozen (without the cheese) for 1 month. Serve spoonfuls of the vegetarian mixture on small, crisp tostadas with a sprinkling of cheese."