Make slits in the roast and stuff it with garlic slices all over (you may do this the24 hours in advance).
Rub the roast all over with olive oil, then season with salt and pepper.
Place the roast in a shallow roasting pan, fat side up.
Allow the beef to come down to almost room temperature (this will take about 2-1/2 hours).
Set oven to 350 degrees F.
Pour 1/4-1/3 cup beef broth in the bottom of the pan.
Insert a meat thermometer into the center of the roast.
Cook the roast for 40 minutes.
After the 40 minutes of cooking the roast, toss the potatoes in oil and then add to the pan, stirring to coat with the meat juices, then season the potatoes with salt and pepper, continue to cook for about 20 minutes.
After 20 minutes of cooking, add in the mushrooms to the pan, stirring to coat with the juices, and then continue to cook for another 40-50 minutes, depending on how you like your roast (your thermometer should read about 130F).
Remove the roast to a cutting board, and transfer the potatoes and mushrooms to a platter.
Pour the pan juices into a small saucepan and skim off any fat accumulated on top.
Pour the 2 cans of beef broth into the pan juices and bring to a boil; lower heat and let simmer for 3 minutes.
Mix together the soft butter and flour in a small cup, the add into the saucepan with the tomato paste; whisking gently to combine.
Slice the beef and serve with gravy, mushrooms and potatoes.