Preheat an oven to 400 degrees and line an oven pan with baking sheet.
Preparing the éclairs: Bring the water, butter, sugar and salt to a boil in a small saucepan over medium flame. Once the mixture begins to bubble add flour all at once and stir quickly with a wooden spoon until the flour is absorbed in the liquid. Remove from the stove and allow it to cool for 2 minutes.
Mix a little to cool the mixture. Add the eggs one at a time and mix well with a wooden spoon until they are completely absorbed.
Move the dough to a pastry bag with a smooth nozzle ½ inch in diameter and pipe circles 1.5 inches in diameter onto the pan. Maintain spaces between the circles.
Bake for 20 minutes until the éclairs are very puffy and golden – Under no circumstances should you open the oven door! After 20 minutes, open the oven door just a crack and bake for another 5 minutes. Remove the pan and immediately punch a small hole in each éclair with the tip of a knife at the bottom or on the side to allow the steam to be released. Allow them to cool to room temperature.
Prepare the whipped cream and fill: Place the sweet cream, powdered sugar and Biscoff Spread in a bowl and beat well using a manual whisk into a uniform mixture. Assemble the batter and whip for 2-3 minutes until the whipped cream stabilizes.
Move the whipped cream into a pastry bag with a smooth pastry tube nozzle ½ inch in width. Fill each éclair with whipped cream through the hole we cut until the éclairs inflate. Or you can cut the éclairs in half and fill them with a tablespoon.
Glaze: Heat Biscoff Spread in a microwave for 5-10 seconds to liquefy. Dip each éclair in the liquid spread and arrange them on a serving plate. Wait a few minutes for them to cool and serve on the same day.