1 lb ground round
1 cup freshly grated parmesan cheese
2 egg yolks
salt & fresh ground pepper
2 tablespoons butter
1/4 onion, thinly sliced
1 tablespoon olive oil
1 tablespoon butter
1/2 cup heavy cream
1 tablespoon balsamic vinegar
1 In a medium bowl, mix together beef, cheese, egg yolks, salt and pepper and form into 6 patties.
2 Heat 2 tbsp butter in a heavy skillet over medium high heat, brown patties on both sides, reduce heat to medium and cook until juices are pink.
3 Remove patties and cover with foil.
4 Add oil, 1 tbls butter and onion to the pan and cook over medium heat until onion is golden brown.
5 Add cream and vinegar and cook on low 2 minutes.
6 Pour sauce over patties and serve.