Sprinkle plums with Armagnac and leave to soak for at least 6 hours, preferably overnight.
Heat milk, sugar and 60 g butter while stirring until butter and sugar have dissolved. Leave to cool for about 10 minutes.
Grease an ovenproof casserole dish (approx. 23 x 30 cm; approx. 7 cm high). Mix eggs and 125 g flour with the whisk of the hand mixer. Slowly stir in the milk mixture and pour the dough into the mould.
Dab plums dry. Dust with approx. 1 tbsp. flour and spread on the dough. Bake in the preheated oven (electric cooker: 175°C/circulating air: 150°C/gas: level 2) for approx. 45 minutes. Let cool off. Dust with icing sugar.
Drinks tip: Café au Lait.