Put the sugar and water in a saucepan, place on the heat and once the temperature has reached 121°C, remove from the heat. In the meantime, place the egg yolks in a bowl, beat them lightly and then slowly add the water and sugar mixture continuing to whisk until the mixture becomes completely cold. Steam cook the pumpkin, sieve it and add it, together with the grated grapefruit peel, to the whipped egg and sugar mixture (do not throw away the pumpkin cooking water).
In another bowl, lightly whip the cream (it must not be whipped until stiff) and also incorporate it into the mixture by stirring delicately from top to bottom. Put the mixture into your own moulds (small ones are preferable) and leave to set in the freezer. As for the sables, put the sugar and water in a pan, and heat. When the mixture starts to boil, add the previously coarsely chopped roasted chestnuts and cook over a low heat, stirring constantly until you see sugar crystals forming around each individual chopped chestnut. Melt the mascarpone with the milk in a pan, whilst simultaneously melting the chocolate in a bain-marie. Add the chocolate to the mascarpone, stir and then remove from heat.
To cook the pasta, pick back up the pan used to steam the pumpkin, then add the grapefruit juice, orange peels, chilli pepper and a pinch of salt. Once it has been brought to the boil, cook the tagliolini for 3/4 minutes, drain them and season with the mascarpone sauce. Serve the tagliolini with the currant sauce, sables, pumpkin semifreddo, edible flowers and mint.