Beef with tenderloin

1 1/2 lbs beef tenderloin 1 teaspoon dried parsley 1 teaspoon dried basil 1 teaspoon black pepper 1 teaspoon dried oregano 1 teaspoon whole grain mustard 1[...]

4 tablespoons butter , more if needed 1 1/2 lbs beef tenderloin , cut in strips 1 large yellow onion , thinly sliced 14 ounces mushrooms , sliced 2[...]