Melt 80 g of butter in a saucepan, stir in 2 tablespoons of flour, and toast for 1-2 minutes into a light roux.
Pour in the 250 ml of strong black coffee, stirring constantly to keep it lump-free, then cook over medium heat until it forms a thick cream that pulls away from the side of the pan (about 5 minutes).
Transfer to a bowl and let cool completely, stirring occasionally.
Stir in 150 g of sugar, then work in 6 egg yolks one by one, until the mixture is smooth and fluffy.
Whip 6 egg whites into a stiff foam, and fold gently and loosely into the coffee cream.
Pour into a buttered, floured pudding mold of about 1.5 liters, and seal with a lid or foil.
Set in a pot half-filled with boiling water so the water reaches halfway up the mold, and steam, covered, over low heat for 45 minutes, until a skewer inserted comes out without raw batter.
For the sauce, bring 200 ml of strong coffee to a boil with 3 tablespoons of sugar, simmer lightly into a syrup, then let cool to lukewarm.
Turn the pudding out onto a plate, and serve with the warm coffee sauce.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.