Mix together the saffron, stock and ½ teaspoon of salt in a jug and set aside to infuse.
Heat the olive oil in a large, wide pan over a low heat. Add the onion and cook gently for about 10 minutes until it is soft.
Add the chopped tomato and garlic and cook gently for another 5-10 minutes until soft.
Add the sliced peppers, smoked paprika, bay leaves, thyme, rosemary and tomato puree and fry for 2 minutes.
Add the wine, turn up the heat and simmer until it has almost all evaporated.
Add the rice, green beans, peas, butter beans and stock mixture. Stir until it is well combined then cook at a gentle simmer for about 20 minutes until the stock has all evaporated. Do not stir the paella while it is cooking. Rotate the pan occasionally so that it cooks evenly.
Give the paella a brief stir and check whether the rice has cooked through. If it is not fully cooked, drizzle over a bit more stock or water and continue to cook over a low heat until it is just al-dente.
If you want the paella to have a crispy base (socarrat), turn up the heat a little and cook until you hear a gentle crackling sound then remove the pan from the heat. Be careful not to go too far however or the paella will burn. This step is not necessary but it is tasty!
Season to taste with salt, pepper and a squeeze of lemon juice. Arrange the artichokes on top of the rice and cover the pan with a lid or tin foil. Set aside to rest for 10-15 minutes before serving.