Cut the cauliflower into florets and discard the core. Place the florets in a food processor and pulse until they resemble rice grains. Alternatively, you can use a box grater to grate the cauliflower into rice-sized pieces.
Heat the oil in a large skillet or wok over medium-high heat. Add the minced garlic and chopped onion, and sauté for 2-3 minutes until softened and fragrant.
Add the diced mixed vegetables to the skillet and cook for 3-4 minutes until they begin to soften.
Push the vegetables to one side of the skillet and pour the beaten eggs into the empty space. Allow them to cook undisturbed for a minute or two until they begin to set. Then, scramble the eggs with a spatula until cooked through.
Stir in the riced cauliflower and cook for 5-7 minutes, stirring occasionally, until it is tender and cooked through.
Add the soy sauce (or tamari) and oyster sauce to the skillet, and toss everything together until well combined. Cook for an additional 2-3 minutes, allowing the flavors to meld.
Season with salt and pepper to taste.
Garnish with chopped green onions and sesame seeds, if desired.
Serve hot as a main dish or side dish.