Heat the vegetable oil in a large skillet or wok over medium-high heat. Add the minced garlic and cook for 30 seconds until fragrant. Add the grated beetroot and cook, stirring occasionally, for about 5 minutes until slightly softened. Add the shredded cabbage and cook for another 5 minutes, until tender but still crisp. Stir in the white beans, soy sauce, salt, and pepper, cooking for an additional 3-4 minutes to combine flavors. Toss in the sliced green onions just before removing from heat. Serve hot, garnished with chili flakes or sesame seeds if desired.