Begin by making the cream filling. In a medium bowl, whisk together the egg yolks and granulated sugar until they become pale yellow. Then, sift in the flour and cornstarch and whisk until smooth. Set aside.

In a small pot over medium heat, stir together the milk and vanilla. Once it begins to simmer, remove it from the heat and carefully whisk the warm milk mixture into the egg mixture bit by bit. (Be sure to incorporate the warm milk very slowly, to avoid scrambling the eggs.)

Pour everything back into the pot and bring to a simmer, continually whisking for about two minutes. Once thickened, strain the cream through a sieve into a clean bowl. Cover the warm pastry cream directly with plastic wrap to avoid a skin from forming, and place into the fridge until completely cooled.

As the pastry cream cools, whip together the heavy cream and powdered sugar until light and fluffy. Then, gently fold the whipped cream into the cooled pastry cream until light and fluffy. Set aside.

Next, make the éclairs. Preheat the oven to 475 degrees F. In a medium pot, heat the water, milk, butter, sugar, and salt until the butter has melted. Then, add in the cup of flour and stir continually until a large ball of dough firms and begins to dry out & pull away from the sides of the pot (about 3-5 minutes.)

Place the ball of dough into the bowl of a stand mixer and allow it to cool for 10 minutes. Once the dough has cooled, beat in the eggs one at a time and continue to mix until the dough becomes smooth and creamy. Divide the éclair dough into two parts, leaving one part plain and mixing one tablespoon of cocoa powder into the second part (this will create your chocolate éclair shells.)

Transfer the éclair dough into a piping bag fitted with a large round tip and line a couple of baking sheets with parchment paper. Carefully pipe out long strips of the vanilla and chocolate éclair batters until all of the dough is used up. Then, bake in a 425 degree F oven for 15 minutes, rotating the pans halfway through to allow for even browning. After the first 15 minutes are up, reduce the oven heat to 350 degrees F and continue baking the éclairs for 15 more minutes. Once done, set the éclairs aside and allow them to cool.

Next, create your customized fillings and glazes. Start with the fillings: grab your cooled cream filling and divide it into 5 separate bowls. In one bowl, mix in a tablespoon of funfetti cake mix. In another, add a tablespoon of mini chocolate chips. In the third bowl, mix in a tablespoon of cocoa powder. Keep the last two bowls of cream filling plain. For the glazes: combine 2 cups of powdered sugar with ¼ cup of heavy cream. The glaze should be thin enough to spread easily, but thick enough to keep from running off the éclair. Divide the glaze into 4 bowls. In the first, mix in a tablespoon of funfetti cake mix. In the second, mix in a tablespoon of cocoa powder. Leave the last two bowls of glaze plain. After the glazes are made, make your ganache (for the Hostess Cupcake éclair.) Combine ½ cup of very warm heavy cream with ¼ cup of chocolate chips. Stir until melted, shiny, and smooth.

Lastly, assemble your éclairs. For the Cosmic Brownie éclair, pipe a chocolate éclair shell full of the chocolate cream filling. Top with the chocolate glaze and candy coated chocolate chips. For the Hostess Cupcake éclair, pipe a chocolate éclair shell with plain vanilla cream filling. Top with the chocolate ganache and carefully pipe the classic “Hostess Cupcake swirl pattern” using a small round piping tip and some extra thick vanilla icing. For the Dunkaroos éclair, fill a vanilla éclair shell with the funfetti cream filling. Top with funfetti glaze, rainbow sprinkles, and crushed Dunkaroo cookies. For the Sno Ball éclair, pipe a chocolate éclair shell with plain vanilla cream filling. Top with vanilla glaze and cover completely with hot pink coconut (coconut flakes mixed with a few drops of hot pink food coloring.) Lastly, for the Cookie Crisp éclair, pipe a vanilla éclair shell with mini chocolate chip cream filling. Top with vanilla glaze, crushed Cookie Crisp cereal, and mini chocolate chips.