Membrillo con Queso (Quince Paste with Manchego)

Instructions

1. Rub the fuzz off the quinces under running water. Peel, quarter and core them, then cut into 1-inch (2.5 cm) chunks, putting them straight into a heavy pot with the water and lemon juice so they do not brown.
2. Cover and simmer over medium-low heat, stirring now and then, until the quince is completely tender when pierced, 25 to 35 minutes.
3. Purée the quince with its liquid in the pot with an immersion blender (or in a food processor) until very smooth. Weigh the purée; you should have about 900 g. Use about the same weight of sugar, up to the 800 g listed (less if your purée weighs less).
4. Stir the sugar into the purée and cook over low heat, stirring often with a long wooden spoon and more constantly toward the end, until the paste turns a deep coral-red, pulls away from the sides, and a spoon drawn across the bottom leaves a clear trail for a few seconds, 60 to 90 minutes. Wear an oven mitt; the thick paste spatters.
5. Line the loaf pan with parchment paper. Scrape the hot quince paste into the pan, smooth the top and let it cool completely at room temperature, about 2 hours.
6. Cover and refrigerate until firm enough to slice cleanly, at least 12 hours.
7. Turn the membrillo out and cut into 1/4-inch (6 mm) slices. Cut the Manchego cheese into slices of the same size and serve each slice of quince paste on or beside a slice of cheese.