Shell the peas and refrigerate until needed.

In a saucepan over medium heat, melt 2 tablespoons of the butter. Add the onion and sauté gently until translucent, about 2 minutes. Add the water chestnuts and cook, stirring, about 2 minutes. Set aside.

In another saucepan combine the water, the remaining 2 tablespoons butter and the salt. Bring to a boil and add the peas. Cover and cook until just tender, 2 - 3 minutes.

Meanwhile, return the saucepan with the onions and water chestnuts to medium-low heat. Add the mint and cream and stir until heated through.

When the peas are tender, drain well and combine with the onions, water chestnuts and cream. Toss well. Season to taste with salt, transfer to a warmed serving dish and serve.