1. Pour oil in the middle of a paella pan, then sprinkle salt around the edge of the oil. Heat the garlic over a medium heat, then remove the garlic and set aside.
2. Mix a quarter of the salt into the oil and add the red pepper. Fry until crisp. Remove and set aside along with the garlic.
3. Bring another quarter of the salt into the oil and add the asparagus. Fry until crisp then remove and set aside with the pepper.
4. Finally, bring in the last bit of salt to the oil and add the mushrooms. Fry until beginning to soften then remove and reserve with the other vegetables.
5. Add the tomato purée to the pan and simmer over high heat for about 2 minutes until reduced and very thick. Add in the vegetable stock and water and bring to a boil. Add the rosemary, paprika, bay leaf and soy sauce and boil for 5 minutes.
6. Reduce heat to low and add the saffron and 1 teaspoon of salt. Leave for 30 minutes on the lowest heat. Ensure it is not simmering.
7. After 30 minutes remove the rosemary and bay leaf and add the rice and spread it out around the pan. Raise heat to high and boil for 7 minutes. Reduce heat to medium and simmer for 6 minutes. Add the fried vegetables, quartered artichoke hearts and sun-dried tomatoes to the rice and reduce the heat to medium-low. Cook for 6 minutes.
8. Remove from heat and let rest for 5 minutes. Serve with lemon slices.