Heat 1 tablespoon oil in a large skillet over high heat. Add broccoli and a pinch of salt, and stir-fry for 3-4 minutes, until slightly charred. Pour 1/4 cup water into pan, and cover. Cook for another 3 minutes, until broccoli is tender. Uncover, and let any remaining liquid burn off. Add garlic, and toss well to coat broccoli. Cook for 30-60 seconds, until garlic is fragrant. Scoop broccoli into a large bowl.
Add remaining 1 tablespoon oil to the pan, and swirl to coat. Add carrot and onions, and stir-fry 2 minutes. Stir in cabbage, and cook 3-5 minutes, until wilted and slightly charred. Toss shrimp and broccoli with cabbage mixture. Microwave tortillas/crepes for 20 seconds on a plate covered with a clean dish towel.
While cabbage is cooking, whisk together soy sauce, 1 tablespoon water, cornstarch and Sriracha in a small bowl. Stir soy sauce mixture into cabbage mixture with a pinch of salt, and toss to coat. Serve with plum sauce and tortillas or crepes.