Ate de Membrillo (Mexican Quince Paste)

Instructions

1. Put the whole quinces in a large pot, cover with water and simmer until a knife slides easily into the center, 35 to 45 minutes. Drain and let cool until you can handle them, about 20 minutes.
2. Brush the 8-inch (20 cm) square pan with the neutral oil and line with parchment, leaving an overhang.
3. Peel, quarter and core the quinces, discarding the hard gritty core. Blend the flesh until very smooth, adding up to 60 ml water only if the blender needs it; you should have about 1 kg puree.
4. Combine the puree, granulated sugar and lime juice in a heavy wide pot and stir over medium heat until the sugar dissolves, about 5 minutes.
5. Lower the heat to medium-low and cook, stirring constantly with a long wooden spoon and scraping the bottom, until the paste darkens from gold to deep coral-red and becomes very thick and glossy, 50 to 60 minutes. It is ready when it pulls away from the sides of the pot and a spoon dragged across the bottom leaves a clear path for a few seconds.
6. Scrape the hot paste into the pan and smooth the top with an oiled spatula.
7. Let it cool and set uncovered at cool room temperature for 24 hours, until firm.
8. Lift out by the parchment and cut into 24 bars.