Heat the olive oil in a skillet over a medium/high heat and add the pork loins. Cook for 4 minutes each side or until browned all over and completely cooked through. Set aside and keep warm.
Finely dice the shallot and add to the skillet, sweating for a minute until tender.
Finely chop the rosemary and add to the skillet, cooking for a minute more to soften.
Add the creme fraiche, mustard, salt and pepper. Stir well to combine, melting the creme fraiche. Simmer for a few minutes until hot through. Serve the sauce on top of the pork loins.