Place the clam juice and squid ink in a small sauce pan. Bring to a gentle boil and then lower the heat to let it cook for another 1 minute. Remove from the heat and set aside
Place the ingredient for sofrito in a food processor and process until smooth. Preheat a large paella pan or if you don't have one like me, I just use cast-iron skillet. Add in cooking oil. Add in the sofrito and cook for about 5 minutes. Add in the smoked paprika, pinch of salt. Add in the rice and stir to combine. Add in the clam and squid ink broth into the pan. Spread the rice evenly on the surface of the pan. Bring the broth to a boil and then lower the heat to maintain a gentle steady simmer. The rice will gradually absorbs the broth and try not to disturb the rice while cooking, this will take about 10 minutes or so. Arrange the mussels pieces on top of the rice and let them cook again for another 5 minutes. If the rice is cooked but the mussels are still not cooked through, cover the pan with aluminum foil and lower the heat and let it continue to cook until the mussels are cooked through. The cooked mussels will open up and discard the ones that aren't.
While the paella is cooking, preheat another non-stick pan with 1 Tbsp of oil. When the pan is hot enough, gently place the scallops about 1 inch apart, season with a bit of salt and let them sear about 2-3 minutes on each sides. Remove from the pan and arrange on top of the cooked paella. At this point, the rice should be cooked through and the rice at the bottom of the pan should have some short of caramelization or stickiness to the pan. Remove from the heat and cover with the aluminum foil for 5 minutes before serving. Add some fresh cilantro leaves and fresh diced tomatoes for color contrast. Serve with lemon wedges
Since the whole presentation of the dish is "dark" in color, I like to add fresh bright colors like cilantro leaves and fresh diced tomatoes for that color contrast and It helps to see the black rice better too, I think ;)