To a bowl, add the dry pea crumbles. Pour 1 cup of boiling water over the crumbles. Cover the bowl, and let it sit for 5-8 minutes until the water is completely soaked.
Slightly tilt the bowl and squeeze the crumbles using the back of a spoon to discard any excess water. Add the tomato paste, paprika, sumac powder, cumin powder, 3/4 tsp salt, and black pepper to the crumbles. Mix well.
Drizzle 2 tbsp of olive oil into a skillet over medium heat. Add the seasoned pea crumbles to the pan and spread it evenly—Cook for 3 minutes without stirring to develop some color. Stir, then cook for another 2 minutes.
Drop the heat to low and pour in the vegetable broth. Cover the skillet and let it cook for 10 minutes until most of the liquid has evaporated. Finely chop the parsley, tomatoes, and red onions and add them to the skillet along with the mustard. Turn off the heat, stir, and let the vegetables wilt for around 10 minutes
Meanwhile, prepare the tahini sauce. Add the tahini, 1 Tbsp olive oil, lemon juice, water, and 1/4 tsp salt to a bowl. Whisk until a creamy sauce forms.
Portion out the veggie shawarma into 4 microwave-safe containers and the tahini sauce into 4 small containers. Chop the mint leaves, and sprinkle over the shawarma. Cover with a lid and store in the fridge for up to 4 days.