Dining In - Copykat recipe

Two years ago while visiting family in Oklahoma I went out to a restaurant in Norman, OK called "Saltgrass Steakhouse"  while there I ordered an entree that was simple, yet filling, and moderately priced.

Unfortunately there are only a few Salt grass restaurants nationwide, so the quest was on to re-create this entree: Beef Tenderloin tips sauteed in a cognac pepper sauce w/ mushrooms over garlic mashed potatoes.
What is "cognac pepper sauce"?  Well just imagine a savoury brown gravy that has black pepper and cognac in it...simple huh?!   You don't have to worry about the mashed potatoes, they're really not the super star. 
My version is as follows:  This will serve two people

8 ounces tri-tip sirloin cut into bite size pieces
2 Tbsp butter, divided
1 Tbsp flour
1/2 tsp garlic salt
1/8 tsp freshly ground black pepper

Place flour, garlic salt, and black pepper in a ziploc bag.  Add the beef and shake to coat.
In a cast iron skillet over medium heat, melt 1 Tbsp of the butter.  Add the beef, and cook stirring frequently.
Add in the sliced mushrooms and remaining butter, stir until mushrooms are tender.

Cognac Pepper Sauce
2 Tbsp flour
2 Tbsp butter
1/2 tsp kitchen bouquet browning and seasoning sauce
1/2 tsp Worcestershire sauce
10 oz beef broth or beef stock
1 Tbsp Cognac
1/2 tsp freshly ground black pepper

In a medium sauce pan over medium high heat, melt the butter.  Whisk in the flour until a blonde roux has developed.  Slowly pour in half of the beef broth, whisking to combine.  Add in the browning sauce, the worcestershire sauce, and remaining beef broth whisking to combine.  Add in the black pepper.  Stir to combine.  Continue stirring until slightly thickened.  Add in the cognac during the last minute of cooking, stir to combine.

Serve the beef tips, mushrooms and cognac pepper sauce over your favourite mashed potatoes.