Preheat the oven to 400 degrees Fahrenheit.
Carefully cut the stalks from the mushrooms and finely chop. Finely chop the rosemary and crush the garlic. Heat a tablespoon of the oil in a skillet over a low/medium heat. Add the onion, garlic, mushroom stalks, rosemary and pine nuts. Sweat gently for 3-4 minutes until tender and golden.
Whilst the stuffing is cooking, carefully scoop out the gills of the mushroom with a teaspoon and discard. Brush the mushrooms with the remaining oil then transfer to a shallow oven tray. Bake for 10 minutes until tender.
Finely chop the cranberries and add to a small bowl along with the ground almonds, nutritional yeast, salt and pepper. Stir to combine.
Add the onion and pine nut mixture and stir well.
Divide the stuffing evenly between the two part-cooked mushrooms. Return the mushrooms to the oven to bake for a further 8 minutes or until cooked through and tender and the stuffing is golden.