To butterfly chicken breast, slice horizontally from the thickest side toward the centre of breast, open up and press firmly with the palm of your hand to flatten.
Coat with olive oil, paprika, salt and pepper.
Place in a preheated non-stick pan on a medium heat.
Whilst chicken is cooking blanche the spinach in salted boiling water until it wilts (2-3 mins) and strain.
Turn the chicken when half cooked and finish cooking (this process should take approx 15 mins, depending on how thick it is).
Remove and place in a plate.
On high heat, in the same pan, fry the mushrooms in butter with a little olive oil and season with salt and pepper.
When ready add spinach and feta and toss together for 2-3 mins.
Remove from the heat and serve with the chicken.
You might need to add a few drops of water when cooking the mushrooms in order to de-glaze the pan and extract all of the flavour.