- 2 pounds russet potatoes, peeled and cut into large chunks
- 1 1/2 pounds English peas, or 2 pounds frozen peas
- 2 cups heavy cream
- 1/2 cup (2 sticks) unsalted butter, at room temperature
- 1 tablespoon minced garlic (about 3 to 4 cloves)
- Salt and freshly ground black pepper
- Grated Parmesan, optional
Put the potatoes in a large saucepan with cold water to cover by 3 inches. Salt the water, cover and bring to a boil over high heat. Reduce heat and simmer until tender, about 10 minutes. While the potatoes are cooking, cook the peas in a separate saucepan of salted water. Simmer until just tender, about 3 to 5 minutes. Remove with a sieve and cool on a baking sheet. When the potatoes are done, drain well, scatter on a baking sheet, and let cool for several minutes. In a small saucepan, heat 1/2 cup of the cream until it reaches a boil then simmer for a few minutes. Add the cream to a blender with the cooked peas and puree until smooth. Season with salt and pepper.
Heat 1 tablespoon of the butter in a large saucepan over medium heat until the butter stops foaming and turns a light brown. Add the garlic and cook quickly until pale gold. Add remaining cream, season, to taste, with salt and pepper and bring to a boil.
Reduce the heat to low. Add the remaining butter by tablespoonfuls, stirring vigorously after each addition. In this way, the butter does not melt into a golden puddle. Instead, it forms an emulsion with the potatoes, creating a very smooth puree.
Fold the pea puree into the mashed potatoes and adjust seasoning, as necessary. Instead of salt, the puree can be seasoned with a little grated Parmesan, if desired.