For the devilled kidneys, heat a large frying pan. Once hot, add the butter and, when melted, add the shallots. Cook for a few minutes then add the garlic and cook for a further minute.
Turn up the heat and add the kidneys and cook until golden-brown. Add the mushrooms and cook for two minutes. Deglaze the pan by adding the brandy and scraping the bottom of the pan with a spoon to remove any charred bits.
Add the stock and bring to the boil. Cook until the volume of liquid has reduced by half, then add the cream, mustard, Worcestershire sauce and cayenne pepper. Stir and cook for 2-3 minutes, or until the sauce has reduced and thickened.
Meanwhile, heat a large griddle pan and drizzle the oil over the bread. Place on the griddle pan and cook for a minute on each side, or until bar marks appear on the bread.
For the green salad and sherry vinaigrette, separate the little gem leaves and place in a large bowl. Pour the oils, mustard and vinegars into a small bowl and whisk. Set aside until ready to serve.
Just before serving add the chopped parsley to the kidneys. Place a slice of bread on each plate and spoon the kidneys and mushrooms on top.
Pour the dressing over the salad and toss. Serve the salad next to the kidneys on toast.