Queso de Tuna (Prickly Pear Paste)

Instructions

1. Handle the prickly pears with tongs or thick gloves. Cut off both ends, slit the skin lengthwise and peel it away; weigh the flesh.
2. Pulse the red prickly pears in a blender 2 or 3 seconds at a time, just enough to break them up without cracking the seeds, or mash them in a pot. Press through a fine sieve and discard the seeds; you should have about 1.3 liters of juice.
3. Boil the juice in a wide, heavy pot over medium-high heat, skimming off the foam, until it has reduced by about three quarters and starts to look syrupy, about 60 minutes.
4. Lower the heat to medium-low and stir constantly as it thickens and darkens to a reddish brown, until a spoon drawn across the bottom leaves a clear trail and the syrup reads 240°F (116°C) on a candy thermometer, 30 to 45 minutes.
5. Brush a marble slab or heatproof board and a bench scraper with some of the vegetable oil. Pour out the paste and let it cool until you can touch it, 10 to 15 minutes.
6. Fold and knead it with the scraper and then lightly oiled hands, pulling and folding repeatedly until it turns lighter and opaque, stiffens and no longer sticks to the slab, 10 to 15 minutes.
7. Press the paste firmly into the mold brushed with the rest of the oil and smooth the top. Let it rest at room temperature 24 hours.
8. Unmold and let it air-dry on a rack 24 hours more, turning once. Cut into 12 pieces.