Toss the mushrooms with the garlic, cumin and thyme, a glug of olive oil, and some salt and pepper in a bowl. Put the mixture on a baking tray and bake for 10 minutes or until the mushrooms are browning. Remove and put to one side.
When cooled, place the mushroom mix in a food processor with the other ingredients and blitz until combined and still a bit lumpy. Form small patties with the mix.
Over a medium heat add olive oil to a frying pan and cook each burger for about 4 minutes each side. Serve on wholemeal buns with salad and ketchup.