Heat the oil in a 38cm paella pan over medium-high heat. Add the squid and cook until slightly firm.
Remove and set aside. (If using prawns, cook those until they change color and also set aside.)
Add the rice and cook briefly until the grains are coated with the oil. Pour in the squid ink paella cooking base, stir in the smoked paprika and salt, and bring to a boil. Reduce the heat and simmer for about 10 minutes or until half of the liquid is absorbed. Do not stir the rice.
Position the shellfish and piquillo peppers the way you want them to appear in the final dish. Continue to simmer over medium-low heat for about another 20 minutes until the seafood is cooked through. Turn the pan every few minutes to position the different section over the flame to create that crispy bottom crust, the socarrat.
Remove from the heat, add the squid and prawns (if using) and tent the pan with some aluminum foil for 5-10 minutes to allow the shellfish to open. Garnish with some lemon wedges and fresh parsley and serve immediately.