Peel and dice the russet potatoes into ½-inch cubes. Place them in a large pot, cover with water, and add a pinch of salt. Bring to a boil over medium-high heat, then reduce heat and cook for 12-15 minutes until fork-tender.

Prepare the frozen peas. Once the potatoes are tender, stir in the peas and cook for an additional 3-5 minutes. Drain and set aside.

In a saucepan, melt 2 tablespoons of unsalted butter over medium heat. Add the diced onion and sauté for about 5 minutes until soft and translucent.

Pour in 1 cup of heavy cream. Raise the heat slightly and bring to a gentle simmer, stirring consistently until the cream thickens, about 3-4 minutes.

Combine the drained potatoes and peas with the creamy sauce. Sprinkle with 1-2 teaspoons of dried dill, salt, and pepper to taste. Fold together gently.