In a large pot, place potatoes and add enough water to cover. Cook 13 to 15 minutes or until very tender. Drain potatoes in colander. Return cooked potatoes to pot. With potato masher, mash in hot milk, 4 tablespoons butter, salt, and pepper. Beat with wooden spoon until potatoes are smooth and creamy. Set potatoes aside and keep warm.

Meanwhile, in a medium saucepan, melt the remaining 6 tablespoons of butter. Add the peas and cook until the butter starts to simmer. Add chicken stock and continue to cook until the stock starts to simmer and the peas are heated through, but still a bright green. Pour the pea mixture into a large mixing bowl and mash. Add the hot mashed potatoes. Fold in the fresh mint.

Garnish with a sprig of mint.