Make a quick sponge: whisk the eggs with the sugar until fluffy, then gently fold in the flour and the oil.
Pour the mixture into a buttered, half-sphere (dome-shaped) baking mould, and bake at 180°C for about 15-18 minutes, until risen and a skewer comes out dry.
Remove from the mould, let cool completely, then scoop out the centre of each dome with a teaspoon, leaving a hollow.
For the filling, whip the cream to stiff peaks, and gently fold in the icing sugar and the dissolved instant coffee or espresso.
Fill the hollowed-out domes with the coffee cream, then press two domes together to form ball-shaped puffs.
Melt the chocolate with the coffee and the butter over a bain-marie, stirring until smooth and glossy.
Dip the coffee puffs into the chocolate glaze so they are fully coated, like a mocha cake.
Chill in the fridge for at least 30 minutes, until the glaze sets, then serve.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.