To make the mayonnaise place the garlic cloves in a saucepan along with the oil. Place over a low heat for 20 minutes to infuse and slowly cook the garlic. Set aside to cool completely.
Place all of the ingredients except the thyme leaves into a narrow jug or bowl. Use a stick or immersion blender to combine the ingredients. You’ll notice that almost immediately the mayonnaise will begin to emulsify. Blend until combined. You can see step by step photos of the process here.
Taste and adjust the seasonings as necessary. Refrigerate.
Rinse the quinoa well in a fine mesh sieve under cold running water. Place in a saucepan with the water and a pinch of salt and bring to the boil. Cover and cook for 12 to 20 minutes. I've found Australian Organic Quinoa cooks particularly quickly (12 minutes), others take up to 20 minutes or even longer. Check after 12 minutes to see if the quinoa is tender and you can see the little quinoa curlicues. Set aside to cool.
Heat a large frying pan over a medium low heat and 2 tsp olive oil and add the onions cook until lightly golden. Remove from the pan and place in a large bowl. Increase the heat to medium high and add another 2 tsp of olive oil. When the pan has come to heat add the mushrooms, garlic and thyme and cook for 2 minutes. Add the soy sauce and cook for a further 2 minutes or until the liquid has almost evaporated. Place in the same bowl as the onions and leave to cool.
Add the cooled quinoa to the bowl along with the onions and mushrooms. Add the breadcrumbs and parsley and mix to combine. Test and adjust seasonings with sea salt and pepper as necessary. Add the beat egg and mix until well combined.
Form the mixture into patties (I find I get around 10 patties out of the mixture) and refrigerate for 30 minutes.
Return the frying pan to a medium low heat and add enough olive oil to just coat the bottom of the pan. Place the patties in the frying pan and cook for 7 to 10 minutes on each side until golden brown.
Enjoy the burgers on fresh bread tools topped with a slice of cheddar cheese along with your favourite salad toppings and a dollop of garlic and thyme mayonnaise or ketchup.