Melt 2 tbsp butter in small frying pan. Add onions and saute until they are tender, about 5 minutes.

In a small saucepan, add just enough water to cover the bottom and keep the peas from scorching, about 60 ml/4 tbsp. Add the peas and onion. Cover and cook over medium heat until peas are tender, 5—10 minutes, depending on size and freshness. If the butter is not at room temperature, melt it while the peas are cooking. When the peas are done, drain them, then add the butter and mint.

Toss and serve immediately.