The Correct Consistency for Choux Pastry
The amount of egg needed for a successful Choux pastry is determined by how much can be absorbed by the flour (which can vary slightly from batch to batch) and the ratio between the water, flour and eggs in a particular recipe, and it is important to get the balance right. If too much egg is added or if it is added too quickly, the Choux's ability to rise when baked will be affected. Similarly, if not enough egg is incorporated, it won’t puff, causing it to be dense inside. But how can you tell if you have added the right amount of egg? The clue is in the consistency of the final Choux pastry.
When adding the egg, incorporate three-quarters of the quantity specified in the recipe first (in a number of batches). Then add the remaining egg just a teaspoonful at a time, beating vigorously after each addition. When enough egg has been added the mixture will be glossy and thin enough that a large spoonful will fall heavily from the spoon in one lump (without shaking or tapping the spoon on the side of the saucepan), but thick enough that it doesn't slide off easily. If you get this consistency right, it will make all the difference to how light, airy and well risen your Choux will be for your éclairs, gougères, profiteroles, Paris-Brest and croquembouche!