Cut the pork fillet in half lengthwise and cut a deep pocket into each piece.
Grate the feta cheese, then mix it with the red pesto, cream cheese with herbs, Provencal mustard, fresh thyme, herbs Provence, and balsamic vinegar until well combined. Divide the mixture evenly and fill the two pockets.
Fold the fillet pieces closed and place on a baking sheet. Bake in a preheated oven at 200°C (392°F) for 30 minutes until the pork reaches an internal temperature of 63°C (145°F).