To make the teriyaki sauce, place all the ingredients except the cornstarch and water to a small saucepan. Mix the cornstarch and water together to make a slurry, then add this to the saucepan. Heat on a medium heat until the mixture is thickened, then transfer to a cool bowl.
Preheat the oven to 200°C. Chop the cauliflower into florets and toss with the sauce until completely coated. Line a flat baking tray with greaseproof paper and spread out the cauliflower evenly. Bake for 20-25 minutes until the cauliflower is completely cooked through.
Blend all the ingredients for the avocado sauce, except the water, until smooth. Add water if you like to thin out the sauce until you have a consistency you like.
Assemble your tacos with the cauliflower, sauce and top with some shredded red cabbage, fresh coriander (cilantro), spring onion and sesame seeds.