Venison Salisbury Steak

Ingredients

• 1/4 cup oil
• 1 pound venison, cut into cubes
• 1 (16 ounce) package buttery round crackers, crushed fine
• 1/4 teaspoon garlic powder, or to taste
• onion salt, or to taste
• salt and pepper to taste
• 2 cubes beef bouillon
• 1 cup boiling water
• 1 egg
• 1 medium onion, sliced
• 1 (4.5 ounce) can sliced mushrooms
• 1 tablespoon cornstarch
• 1/4 cup cold water