Heat the butter and oil in a large frying pan. Add the leeks and gently cook for 5 minutes, until softened but not coloured. Add the garlic and thyme, and cook for a further 2 minutes.
Add the quinoa and stir well so it's coated in the oil. Add the wine and bubble off rapidly. Add the stock to a separate medium pan and gently simmer. Add a ladle of stock to the frying pan, then simmer and stir until almost all of it has been absorbed. Continue to add the stock a little at a time.
When all the stock has almost been absorbed, add the peas and simmer for another 5 minutes until the quinoa is tender. Season to taste, then stir in the parsley and lemon juice and serve in a bowl scattered with the parmesan.