Pat steaks dry and season both sides with kosher salt.
Coarsely crush peppercorns in a sealed plastic bag with a meat pounder or bottom of a heavy skillet, then press pepper evenly onto both sides of steaks.
Heat a 12-inch heavy skillet (preferably cast-iron) over medium high heat until hot, about 3 min, then add oil. Swirl skillet to lightly coat the entire skillet.
Saute steaks in batches (2 at a time). DO NOT TOUCH - this lets them brown nicely and makes all the difference. Cook for 6 min and flip and cook for another 6 minute for medium rare steaks. Repeat with remaining 2 steaks.
Transfer cooked steaks to a heatprook platter and keep warm in the oven.
After all 4 steaks are cooked pour off fat from skillet if any, then add shallots and half of the butter. Cook over medium low heat, stirring and scraping up any brown bits from bottom of the pan until the shallots are well browned all over, 3-5 minute.
Remove skillet from heat and add Cognac. (If you add while on the burner it may ignite.) Boil, stirring until liquid is reduced to a glaze, 2-3 minute.
Add cream and any meat juices that have accumulated on the platter in the oven. Boil sauce, stirring occasionally, until reduced by half, 3-5 minute
Add the other half of the butter and cook over low heat swirling the skillet to melt and incorporate the butter.