Pressure Cook
Heat butter on sauté function medium; add onion and soften for 2-3 minutes
Stir in the risotto rice to coat with the butter & onion mixture
Add the white wine; allow to cook for a further minute allowing some of the alcohol to evaporate
Turn off sauté function; stir in the vegetable broth & lemon juice (retain zest for later)
Secure the cooker lid, seal pressure valve; cook on Manual/Pressure for 8 minutes.
Meanwhile, in a small bowl stir together the egg yolk, parmesan, thyme, & lemon zest
Vent cooker with Quick Pressure Release; stir the egg & cheese mixture into the cooked risotto and serve