Heat the oil in a pan and fry the onion
for a few mins, until soft. Add the garlic
and paprika, and cook for 1-2 mins until
fragrant. Add the pepper and mushrooms,
and fry for 5-8 mins until softened.
Add the vinegar, boil to reduce until
almost evaporated, then pour over the
stock and bubble for a few mins until
thickened slightly. Add the beef and cook
for 2-3 mins depending on how rare you
like it, then stir in the fromage frais and
season. Serve with rice or tagliatelle.