In cast iron skillet add olive and brown beef scraps and pepper. Once beef begins to brown add onions. When onions begin to brown add garlic and stir to loosen brown bits in skillet. 

Once mixture is browned, deglaze with 1/2 c. stock. Continue to scrape bottom of skillet until most browned bits are incorporated into gravy. Stir in rest of stock and bouillon mixture. 

Add the flour and stir continuously using figure-eight motion to fully incorporate butter and flour.

After about 5-7 minutes the roux should change to a blond color.

Slowly add broth mixture to roux. Whisk constanting until gravy is lump free and reaches desired thickness.

Add milk and/or water if gravy becomes to thick.

Taste and add salt and pepper if needed.

**Once you slice the tenderloin it will release a lot more juice that can be added to existing gravy for added flavor.