Read through the recipe twice before starting and measure all your ingredients in advance. Go back and watch my full video tutorial, read my expert tips and extended instructions with photos. This recipe is made in steps and not all at once.

The pastry cream needs a few hours to cool down and set. I recommend making it the night before or the morning of. In a large bowl, whisk together egg yolks and sugar until light yellow in color.

Then, add corn starch and whisk until smooth and thick.

Heat milk and vanilla over medium/low heat until steam forms but NOT simmering. This takes less than 2 minutes.

Put a fine mesh sieve over the egg mixture and SLOWLY pour the warmed milk into the egg mixture WHILE continuing to whisk the egg mixture. Only a little bit at a time. Do not stop whisking while you add the milk. Too fast and you'll scramble the eggs.

Pour the whole mixture through the sieve a second time back into the pot. Gently whisk continuously for 5 to 7 minutes until thickened. Within a few minutes, the mixture will already start to thicken.

Once it starts to stick to the pot, whisk vigorously to smooth out the mixture. It will be thick! Remove from the heat.

Add butter and whisk together until combined. It may separate at first but it will come together as you whisk.

Press down the surface and directly cover with cling wrap or plastic wrap to prevent a top layer of dry skin from forming. Allow it to cool at room temperature. This will take a few hours. If you'd like to, make the pastry cream ahead of time and refrigerate for up to one day. Before using, give it a whisk to smooth out the texture as it will have set into a firm, thick custard.

Preheat the oven to 375°F / 190°C.

In a medium saucepan, combine butter, water, sugar and salt. Heat until butter is melted and mixture is simmering.

Add the flour all at once. Stir vigorously with wooden spoon or rubber spatula until the mixture forms into a smooth ball and pulls away from the sides. There should be film sticking on the bottom of the pan. That's when you know it's ready. Remove from the sauce pan into a bowl. Set aside to slightly cool for 5 minutes. It should still be warm to the touch.

Use an electric hand mixer or a stand mixer with a paddle attachment, to beat one egg at a time until fully combined.

By the last egg, the dough will become smooth, shiny, sticky and thick.

Prepare the springform pans with parchment paper on the bottom and butter the sides with softened butter. Equally divide the dough into two springform pans. If you only have one pan, bake one layer at a time.

Spread the dough evenly, all the way to the corners. Then, use the back of a spoon to create pockets and uneven divots of dough that lift up.

Bake for 28-30 minutes until puffy and light, golden brown. Cool for 5 minutes in the pans, then remove and set aside to completely cool on a wire rack.

Only when you're ready to assemble and serve the éclair cake should you make the whipped cream and complete this step. Place the heavy whipping cream and powdered sugar in a large mixing bowl. Use a hand mixer or stand mixer and whisk until stiff peaks form. Fold in ⅓ of the whipped cream at a time.

Line the edges of spring form pan with parchment paper for easy release of the cake. Add one éclair layer, then all the filling and top with the final éclair layer. Make sure the filling is spread evenly to the edges of the pan.

Cover the entire cake with plastic wrap and refrigerate for at least 2 hours in the springform pan. Keep in the refrigerator until ready to slice and serve. This cake is meant to be cut into thick slices in order to maintain the layers and cream in place. Don't worry, you'll thank me later for that. Best served chilled.