I started off with my family's favorite recipe for homemade spaghetti sauce, which is very good but a bit mild for my preference. So I kept adding certain ingredients until I was satisfied, and I ended up with the recipe posted here. I have added red pepper flakes on occasion too, but that makes the sauce a bit spicy and "over the top" for my kids.
In a medium skillet, brown the sausage (or beef) with the chopped onion until no pink remains in the sausage and the onion is transparent. Drain excess grease.
In the meantime, heat oil in a kettle or stock pot, and sauté the minced garlic, mushroom pieces, and green pepper in the oil until the pepper is tender. Add remaining ingredients, including enough mushroom juice or water to reach the right consistency. Cover; let sauce simmer over low heat for 15 minutes.
Add the browned meat/onion mixture to the kettle. Cover and let the sauce simmer for 20 minutes. Serve over cooked and drained spaghetti noodles.