2chicken carcasses1 eachonion, carrot and celery stalk, coarsely chopped1garlic head, halved horizontally10 gmdried porcini mushrooms6thyme sprigs8small Swiss brown mushrooms, thinly sliced1 bunchspinach, trimmedTo serve:shaved parmesanMushroom and mascarpone tortellini175 gmfield mushrooms, coarsely chopped4golden shallots, coarsely chopped2garlic cloves, coarsely chopped2 tbspolive oil150 gmmascarpone2 tbsp eachfinely chopped thyme and flat-leaf parsleyFinelygrated rind of 1 lemon1 quantityegg-yolk pasta doughFor brushing:eggwash
Preheat oven to 200C. Combine chicken carcasses, onion, carrot, celery and garlic in a large roasting pan and roast, turning occasionally, until browned (50 minutes-1 hour). Transfer to a stockpot, add porcini, thyme and 2 litres cold water, bring to the boil over medium-high heat, reduce heat to medium, simmer until well-flavoured (1½-2 hours). Strain into a saucepan, season to taste and keep warm.
Meanwhile, for mushroom and mascarpone tortellini, process mushrooms, shallot and garlic in a food processor until finely chopped. Heat oil in a large frying pan over medium-high heat, add mushroom mixture, sauté until fragrant (4-5 minutes), transfer to a bowl and cool. Stir in mascarpone, herbs and lemon rind, season to taste and refrigerate until required. Cut pasta into thirty-two 8.5cm-diameter rounds, keep covered. Place a tablespoon of mushroom mixture in centre of each round, brush edges lightly with eggwash, fold in half, pressing edges firmly to seal. Brush corners with eggwash, bring together and press to seal. Cook, in batches, in a large saucepan of boiling salted water until al dente (2-3 minutes), remove with a slotted spoon, divide among hot bowls.
Meanwhile, add mushrooms to chicken broth, simmer until tender (1-2 minutes), add spinach, then ladle over tortellini. Serve hot, scattered with parmesan.