4 medium quinces (about 2 pounds total)
1/4 to 1/2 cup water
2 to 3 cups sugar
Preheat oven to 350°F and lightly oil a 1-quart terrine.
Wash quinces and place in a small roasting pan. Cover and bake until fork tender, about 1 hour.
When cool enough to handle, peel, core, and chop quince and place into a food processor.
Puree pulp with 1/4 cup water until smooth (if mixture is too thick, add remaining 1/4 cup water a little at a time, as needed).
Measure the amount of puree, then transfer to a heavy saucepan and add the equivalent amount of sugar.
Cook over moderate heat, stirring constantly, until it is thickened and begins to pull away from side of pan, about 25 minutes.
Pour into terrine or Pyrex loaf pan.
Smooth the top and once cooled, cover with plastic wrap. Refrigerate at least 4 hours until set.
Run a thin knife around sides of terrine and invert onto a platter. (Quince paste keeps, wrapped well in wax paper and then plastic wrap and chilled, 3 months.)
Serve with crackers and Manchego cheese.