Halve, seed and scoop the avocadoes, then slice into wedges. Slice the mushrooms 1cm thick. Mist with water, then toss gently in rice flour and set aside for 5 minutes.
Place the beer in a large bowl with 2 cups ice cubes. Mix the four, salt, cream of tartar and spices, then sift into the beer, whisking very gently to combine. Dip the avocado and mushroom pieces in, then fry in hot (180°C) vegetable oil for 2-3 minutes, until very crispy. Drain well on kitchen paper, then serve with parsley, lemon and aioli.
COOKS NOTES: * It is important to use avocadoes that are ripe, but still firm.