Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Bring milk, 150 ml water and 1⁄4 TL salt to the boil. Remove from the stove, stir in the puree flakes. Add boiling water to the frozen peas and quench.
Wash and chop the parsley. Whisk eggs and potato mixture, season. Add peas and parsley.
Peel and chop the shallots. Heat the oil in an ovenproof pan. Sauté the shallots in it. Add egg mixture. Leave in the oven for about 15 minutes and serve.