Make 3 slashes in the top of each chicken breast and place the chicken breasts in a shallow ovenproof dish or baking tin. Scatter the mushrooms, garlic and seasoning over the chicken. Spoon 90ml (6tbsp) stock over the chicken. Cover and bake in a preheated oven at 190C / 375F gas mark 5 for 35-45 minutes until the chicken is cooked and tender. Meanwhile, make the sauce. Place the remaining stock, St Ivel Gold Light, flour and wine in a saucepan and heat gently , whisking continuously, until the sauce comes to the boil and thickens. Simmer gently for 3 minutes, whisking. Remove the mushrooms from the chicken using a slotted spoon and set a few aside for garnishing. Add the mushrooms, tarragon and seasoning to the sauce and mix well. Reheat gently, stirring. Serve the chicken breasts with the white wine and mushrooms sauce and the reserved mushrooms scattered over. Garnish with fresh tarragon sprigs and serve with vegtables of your choice. Variation: Use mixed herbs in place of the tarragon.