1. Put the cauliflower pieces into a large cooking pan and add enough boiling water to cover them. Bring it to a boil and cook until tender. You can also steam if you prefer. Drain well. Put in a food processor and pulse until finely chopped.
2. In a saucepan, add 1 tbsp olive oil and fry garlic until fragrant. Add onion, mushrooms and the chopped cauliflower from Step #1 and fry them until wilted. Add the ingredient A (kosher salt, tsuyu, soy sauce) to season. Mix well.
3. Add the butter and mix until the butter is melted, and add the flour and mix to combine evenly. Gradually add milk, stirring constantly as the mixture thickens. Add dash of sugar and mix well. Let it cool in the freezer until firm (about 1h).
4. Shape the mixture into round balls with a slightly flattened bottom, dip in the flour, then beaten egg and coat with breadcrumbs.
5. Place the croquettes into the oil, in batches, and fry until both sides are nicely browned. Remove from the oil and drain on paper towels.