Empty sweet peas and cannellini beans into a saucepan; cook and stir over medium-high heat until heated through and 1/3 of the liquid has evaporated, about 10 minutes. Stir butter into pea mixture until melted, 2 to 3 minutes. Reduce heat to medium.
Stir Parmesan cheese and black pepper into pea mixture. Cook, stirring occasionally, until creamy and thickened, 5 to 10 minutes.
