Gourmet Beef Stroganoff

My step-father-in-law made this for us once out of a gourmet cookbook and it was awesome! We made it too, with just regular button mushrooms, and it was awesome!

Ingredients:
3 ½ tablespoons unsalted butter
1 tablespoon all-purpose flour
1 cup beef stock or store-bought broth
1 pound piece beef tenderloin, trimmed, sliced 1/4 inch thick, and cut into
1-inch pieces, or 1 pound filet mignon, cut into 1-inch pieces
salt and freshly ground black pepper
2 tablespoons olive oil
½ cup thinly sliced shallots
3/4 pound cremini mushrooms, trimmed and halved, or quartered if large
3 tablespoons sour cream, at room temperature
1 teaspoon dijon mustard
2 tablespoons fresh dill
Buttered wide egg noodles

Directions:
1. Melt 1 ½ tablespoons butter in a 1-quart heavy saucepan over moderate hat.
2. Whisk in flour and cook, whisking constantly, for 2 minutes to make a roux.
3. Add stock in a slow stream, whisking constantly, and bring to a boil.
4. Reduce heat and simmer, whisking occasionally, for 3 minutes. Remove from
heat and cover to keep warm.
5. Pat beef dry and season well with salt and pepper. Heat 1 tablespoon butter
and 1 tablespoon oil in a 12-inch heavy skillet over moderately high heat
until foam subsides. Add beef in 2 batches and cook, turning once, until
browned on both sides but still pink inside, about 1 minute per batch. With
a slotted spoon, transfer to a plate.
6. Add remaining 1 tablespoon each butter and oil to skillet and heat until hot
but not smoking. Add shallots and cook, stirring occasionally, until golden
brown, about 3 minutes. Add mushrooms and cook, stirring occasionally,
until liquid mushrooms give off has evaporated and mushrooms are browned, 8
to 10 minutes.
7. Return meat, with its juices, to skillet and stir to combine, then transfer
to a platter.
8. Reheat sauce over low heat, then whisk in sour cream, mustard, dill, ½
teaspoon salt, and 1/4 teaspoon pepper (do not let boil). Pour sauce over
beef and serve over noodles.