Put the beer with the sugar and vanilla in a pot on the stove.
Once the mixture cools a bit, add the oil and then the flour with baking powder in several lots. You have to get a medium soft dough.
From it, shape balls the size of a walnut.
Put 1-2 actual walnuts in each, cover with dough and arrange them in an oven dish laid out with baking paper.
Bake in a moderate 356°F (180 °C) oven and sprinkle with powdered sugar while still warm.