Place the chicken breasts on a cutting board in front of you. With a sharp knife, carefully slice the chicken breasts in half horizontally to create two thin cutlets.
Drizzle the olive oil over the chicken then season with salt and pepper on both sides.
Heat a large skillet or deep frying pan over medium-high heat.
Add the chicken and allow to sear for 2-3 minutes per side until golden brown. Remove and set aside.
In the same pan, melt the butter then cook the garlic and oregano for 30 seconds.
Add the mushrooms and cook until golden brown. Add the spinach and allow to cook for a few minutes until wilted.
Pour in the cream then bring to a simmer. Allow to gently cook for 5 minutes until the mushrooms are cooked and the sauce has reduced slightly.
Season the sauce with lemon juice, salt and pepper and stir in the Parmesan cheese.
Place the chicken back in the pan and cook for another 5 minutes then serve.