Heat a large dutch oven on the stove. Add 1/2 tablespoon olive oil. Once hot, add 1/2 cup diced onion and 1/2 tablespoon garlic. Sauté over medium heat for 3 minutes.
Add ground venison. Sprinkle with a little salt and pepper. Brown meat, breaking into larger pieces, taking about 7 minutes or so.
Remove from the kettle, but keep it warm. Add remaining olive oil. Once hot, add remaining onion, carrots, and celery. Add garlic, salt, pepper, and sage. Sauté for approximately 10 minutes, until just tender, stirring often.
Remove the vegetables from pan. Put the meat and onions back into the pan with the butter.
Once the butter has fully melted, stir in the flour. Cook over medium heat for 1-2 minutes.
The SLOWLY stir in the beef stock, 1/2 cup-1 cup at a time, allowing to thicken as you go.
Stir the vegetables back in, along with the peas and corn.
Bring up to a low boil and stir in the barley. Allow to simmer for 40-50 minutes, until the barley is cooked through. This stew becomes so creamy over the next few days as you allow the barley to settle in.