Preheat the oven to 200℃ (180℃ for fan ovens) or Gas Mark 6. Remove the stems from the mushrooms. Place them on a baking tray, drizzle with olive oil and roast them in the oven for a few minutes or fry them in a frying pan.
Let the mushrooms cool upside down, once cool dry them on kitchen paper. Peel and finely chop the garlic. Sauté the garlic in some oil and stir-fry the spinach in it. Drain the spinach and set to one side and fry the Garden Gourmet Filet Pieces according to the pack instructions.
Boil the cranberries with the syrup and a little water until soft.
Place the mushrooms on a baking tray and fill with spinach, fillet pieces and the grated cheese.
Bake them in the oven for 5 minutes or until the cheese has melted a little. Finish with coarsely chopped walnut, lemon zest, cranberries and thyme.