Pre-heat the oven to 190°C / 375°F / Gas Mark 5.
Gently pull the mushrooms into pieces and mix together.
In a thick-bottomed pot, melt the knob of butter and add the shallots, garlic and all the mushrooms. Cook until they start to soften. Add the rosemary and white wine and bring to the boil. Reduce the wine by two-thirds.
Add the cream and simmer until the mixture has thickened. Remove from the heat and leave to cool for 30 minutes.
While waiting, remove the crusts from the bread and roll the slices flat with a rolling pin. Brush bread with melted butter and line 6 moulds with the bread, making sure there are no spaces. Fill with the mushroom mixture and cover the top with another slice of buttered bread, cut to fit.
Cover the finished Charlotte with aluminium foil and place in a pre-heated oven for 8 minutes. Remove from oven and take off the foil. Place back in the oven for a further 3-4 minutes or until the top is golden brown.
