Sauté the onion

• Heat a generous amount of olive oil in a large pan.
• Add the finely chopped yellow onion and sauté until translucent.

Add the peas and season

• Stir in the frozen peas and sauté for a few minutes.
• Season with salt and pepper.

Add boiling water and simmer

• Pour in the boiling water (about four cups; add more later if needed).
• Let the peas simmer for a few minutes.

Blend half of the peas

• Take out half of the peas with some of the liquid.
• Blend them with an immersion blender until creamy, then set aside.

Cook the pasta with the peas

• Add the ditalini pasta to the pan and stir.
• Stir in the blended peas.
• Simmer until the pasta is cooked and the liquid is mostly absorbed, leaving a creamy center.

Add the cheese off the heat

• Turn off the heat completely.
• Add the grated Pecorino Romano and stir until the sauce is velvety and creamy.

Serve immediately

• Plate the pasta right away, as it thickens as it sits.