Rinse the chicken breasts and tap them dry with kitchen papers. Use a thin-blade knife, slice inside the chicken breasts lengthwise to create a pocket in each one.
For the stuffing, mix well the feta cheese, the cream cheese and the whipping cream until smooth. Add the scalded spinach into the cheese cream, season it with salt, pepper and garlic. Fill the cream into a piping bag and pipe it into the pockets in the chicken breasts. Close the slits with toothpicks or meat needles. Sprinkle salt and pepper on the breast fillets.
Heat a little oil in a pan and brown the meat on all sides. Then place the chicken breasts in a roasting tin lined with greaseproof paper.
Roast them in preheated oven at a temperature of 185°C in 15 minutes. Remove the roasting tin from the oven, leave the roast rest for 5 minutes, then cut them into slices of about one finger thick each. Serve with Greek salad.