Dissolve the yeast in a little bit of the milk. Grease and flour a baking tray.
Sift the flour onto a work surface. Add a pinch of salt, make a well in the centre and crack the eggs into the well. Add the sugar, 8 tablespoons of olive oil and the yeast that was dissolved in milk. Work all the ingredients, adding more milk as needed to get a smooth dough.
Make small balls about 4cm in size and place them on the prepared baking tray. Cover them with a kitchen towel and let them rise until they are doubled in size. Preheat the oven to 170 C / Gas 3.
Bake them in the oven for about 40 minutes or until they are puffy and golden. Let them cool.
In the meantime, make the pastry cream. In a deep saucepan, bring the milk to the boil together with the grated lemon zest.
In a bowl, whip the egg yolks with the sugar and then add the sifted flour a little at a time. Add the hot milk with lemon zest to the egg and flour mixture, whisking. Pour everything back into the deep pan over low heat, constantly mixing, and let it simmer for about 2 minutes. Pour the cream into a cold bowl, add 2 spoonfuls of Centerbe liqueur and let it cool down.
After the cream has cooled down, fill 3/4 of the cream in a pastry bag with a small and smooth tip. Squeeze a little cream on the flat side of the small balls and then put two balls together. Continue in the same way with the rest of the balls.
Add a few spoonfuls of milk to dilute the remaining cream and use the mixture to brush on the balls. Then brush the balls with the Alchèrmes liqueur, and lastly, roll the balls carefully in sugar.