Heat the pan to medium. Use just enough olive oil to coat the bottom of the pan; add a pat of butter.
Put mushrooms in oil and butter cap side down. Brown the mushrooms really good on both sides.
Once the mushrooms are browned, pour beef stock in pan, just enough to almost cover the mushrooms. Pour in wine until mushrooms are completely covered.
Turn down the heat to low and let mushrooms simmer for at least 20 minutes. By then the liquid should be cooked down. Add another pat of butter right before all the liquid cooks out; remove from heat and serve.