When the sofrito is done, add the rice to the pan and cook over medium heat, stirring to combine, 1-2 minutes. Spread the rice evenly in the pan. Increase the heat to high and slowly pour the clam/chicken broth over the rice being careful to leave the rice in an even layer. From this point on, do not stir the rice. Bring to a boil and adjust the heat to maintain a simmer, moving the pan as needed so it bubbles all the way to the edges. Simmer vigorously until the rice appears at the level of the broth, about 8 minutes.