Clean and wash the mushrooms and spring onions. Remove the stems of the mushrooms and chop them finely together with the spring onions. Drain chestnuts well and cut into small cubes.
Remove the crusts from the toast, pluck to fine breadcrumbs. Fry bread crumbs in a teaspoon of hot fat until golden brown. Heat the remaining fat and fry the mushroom stems and onions in it. Add the chestnuts.
Season everything with salt, pepper, soy sauce and Worcester sauce. Fold in bread crumbs. Pour the mixture into the mushroom heads and bake in a preheated oven (electric: 200 °C/ gas: level 3) for approx. 15 minutes.
Arrange the stuffed mushrooms on a plate, garnish with basil and serve hot immediately.