Peel, wash and slice the potatoes. Cook in boiling salted water for 15 minutes. Clean, wash and cut the cauliflower into florets. Clean, wash and cut leek into rings.
Cook the cauliflower in boiling salted water for ten minutes. Add leek for the last two minutes. Drain the vegetables and collect the vegetable water. Quench cold and drain. Drain the potatoes.
Heat the oil in a pot, fry the minced meat in it until crumbly, take it out. Sprinkle flour over the hot frying fat, sauté briefly. Add milk and 200 millilitres of vegetable water while stirring. Bring to the boil, stir in stock and simmer for five minutes.
Place the vegetables, potatoes and minced meat in a small casserole dish (500 millilitres capacity; 15 centimetres diameter). Season the sauce with salt and pepper and pour over the casserole. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15 minutes.
Wash the chives, dab dry and cut into small rolls. Serve the casserole sprinkled with chives and pink berries.