Wash the oyster mushrooms, chanterelle mushrooms, and brown mushrooms, then cut them into bite-size pieces.

Slice the leek white, dice the carrot, and finely chop the shallot.

Heat half of the butter in a large frying pan over high heat, then sauté all mushrooms until browned.

Season the browned mushrooms with salt and black pepper, then transfer them to a bowl.

Melt the remaining butter in the same frying pan, then sweat the leek white, carrot, and shallot over medium heat for 5 minutes.

Pour the water into the pan, then add the fresh thyme and bay leaf.

Whisk the wheat flour with a small amount of hot broth until smooth, then stir the slurry into the pan.

Bring the sauce to a gentle simmer, then cook it for 15 minutes until the vegetables are tender.

Whisk the egg yolk with the heavy cream and lemon juice until fully combined.

Reduce the heat to low, then stir the egg yolk and cream mixture into the sauce without letting it boil.

Return the browned mushrooms to the pan, then heat gently until the first bubble appears.

Remove the thyme and bay leaf, then adjust the seasoning with the remaining salt and black pepper.

Serve the mushroom blanquette over cooked rice, then garnish with fresh parsley.