Making no-bake eclair cake from scratch is not that difficult. The step-by-step instructions will help you create this elegant dessert easily at home. Make it a day in advance.
Combine milk and egg yolk. In a saucepan, mix the sugar and cornstarch. Pour the milk mixture into the sauce pan and bring it to boil over medium heat whisking constantly, about 4-5 minutes.
Remove the pan from the heat and add the butter and vanilla; mix well. Transfer to pudding into a large mixing bowl and cover the surface with a piece of plastic wrap. Chill the pudding for 2 hours in the fridge.
Mix the gelatin and water in a small bowl and heat in the microwave to 15 seconds; cool slightly.
Whip the heavy whipping cream until the soft peak forms. Add the gelatin mixture into the cream and continue to whip until stiff peak forms. Fold the whipped cream into the pudding and combine until the mixture becomes smooth and creamy; set aside.
To make the chocolate ganache
Melt the chocolate chips with the heavy whipping cream in a microwave for about 1-2 minutes, stirring every 30 seconds. Add the corn syrup and stir well. Chill the glaze in the fridge for 15 minutes.
To assemble the eclair cake
Put a few pieces graham crackers to cover the bottom of a 9x13 pan. Spread 1/2 amount of the pastry cream on top. Layer more graham cracker to cover the cream and repeat the step again ending with graham crackers on top.
Pour the chilled cooled chocolate glaze on top and spread to cover evenly on top. Chill the cake for at least 24 hrs and serve cold. The cake will keep fresh in the fridge for about 4-5 days.