Preheat oven to 425° F and while oven is preheating, slice French roll in half horizontally.
In a small pan over medium high heat, melt butter along with olive oil. Sauté onion just till it’s translucent, about 5 minutes. Add flour and cook while stirring for an additional minute. Add remaining ingredients for au jus, bring to a low boil, then remove from heat.
Dip thinly sliced roast beef into hot au jus just to warm it up quickly.
Pile roast beef high on the bottom of your bun.
Top roast beef with provolone cheese and place on an aluminum foil lined pan. Place in preheated oven for 5 to 7 minutes or until cheese has melted evenly.
I knew the first time I ate a roast beef French dip sandwich that I was in love. It’s crazy what memories stick with us from childhood, right? I remember it like yesterday, I had earned some money raking leaves one fall with my buddy and fellow gourmet griller James. After a long day we were hungry enough to eat an old shoe when we rolled into that timeworn Arby’s on Telegraph Road. I ordered the French dip sandwich for the first time and thought I had died and gone to heaven.Anyway, I’ve loved the roast beef French dip sandwich ever since then and have been making a version of it for years. This one is simple and delicious, and with the help of a deli slicer you can shave the smoked roast beef thin enough to read a newspaper through. Side note: a deli slicer isn’t required for this, but it does make things easier. The downside to a deli slicer is the cleaning and storage, but I use it enough to justify it—at least to myself.