Most éclairs recipes in Australia (or the US / UK) will simply tell you to slice the éclairs in half on the length, pipe some cream on the bottom (usually whipped cream) and top it with the second half of the pastry. In French pastry though, éclairs are most often filled from the bottom (or the sides in a commercial environment) using a small piping nozzle such as a bismarck tip or small round tip. Small holes are cut on the bottom of each eclair and the piping tip is pressed into the pastries through it. When the eclair starts to fill heavy with cream and you notice that some of the filling is starting to come out of one of the hole, the eclair is full.