Preheat oven to 325 degrees Fahrenheit.

Place oil and onions in bottom of a large Dutch oven, add the garlic, butternut squash, and flour, and toss to distribute. Smear the mustard over the entire surface of the meat, place on top of the onion mixture and drizzle with soy sauce and honey. Cover top with black pepper.

Cover and bake for two hours.

Remove from oven and cool completely. Slice against the grain into thin strips and rewarm in the sauce for approximately an hour at 300 degrees.