1. Prepare Oven and Baking Sheets:

For the eclairs: Preheat the oven to 400°F (200°C).

Line two baking sheets with parchment paper. Set aside.

2. Make the Choux Pastry: In a medium saucepan, combine ½ cup of water, the cubed unsalted butter, whole milk, granulated sugar, and kosher salt.

Place over medium heat and bring to a boil.

Remove the pan from the heat.

Add the all-purpose flour all at once and stir vigorously with a wooden spoon until the flour is fully incorporated and a smooth dough forms.

Place the pan back over medium heat. Stir continuously until the dough is smooth, forms a thin film on the bottom of the pan, and pulls away from the edges of the pan, 4 to 5 minutes. This step is crucial.

Stir in the vanilla extract.

3. Cool Dough and Add Eggs:

Place the dough into the bowl of a stand mixer (or a large bowl if using a hand mixer).

Allow the dough to cool for 5 to 7 minutes. This prevents the eggs from scrambling.

Using the stand mixer fitted with the paddle attachment (or a hand mixer), beat the dough for 1 minute on medium speed to release some heat.

Beat in the eggs, one at a time, scraping down the sides and bottom of the bowl after each addition. Beat very well until each egg is fully incorporated before adding the next.

4. Pipe the Eclairs:

Transfer the choux pastry dough to a zip-top bag with ½ inch snipped off one bottom corner (or a piping bag fitted with a ½-inch round piping tip).

On one of the prepared baking sheets, hold the piping tip ½ inch above the parchment paper. Slowly pipe logs about 4 inches long and 1 inch wide. Maintain steady pressure.

Stop squeezing and move the tip in a quick circular motion as you lift away to avoid logs that end in a point. If necessary, use a wet finger to smooth any points on the eclairs.

Repeat with the remaining batter and remaining baking sheet, piping 8 to 10 eclairs per baking sheet, leaving space between them.

5. Bake the Eclairs:

Bake the eclairs, one baking sheet at a time, until they are puffed and golden brown, 25 to 30 minutes. Reduce the oven temperature to 350°F (175°C) 10 minutes into the baking time.

Cool completely on a wire rack.

6. Make the Filling:

Meanwhile, make the filling.

In a large bowl, whisk together the whole milk, ½ cup of the sweetened condensed milk, the instant vanilla pudding mix, and the vanilla bean paste until well combined, about 2 minutes.

Allow the pudding to sit for 5 minutes to thicken.

In another large bowl, use a hand mixer (or a stand mixer) to whip the cold heavy whipping cream with the remaining 2 tablespoons of sweetened condensed milk on high speed, beating until firm peaks form.

Fold the whipped cream into the thickened pudding mixture in 3 additions, being careful not to deflate the whipped cream.

7. Fill the Eclairs:

Transfer the filling mixture to a piping bag fitted with a ½-inch round piping tip (Wilton 1A is recommended).

Use a toothpick or the end of a chopstick to poke one hole into the bottom of each cooled eclair.

Insert the piping tip into the hole and pipe filling into each eclair until it is evenly filled.

8. Make the Chocolate Glaze:

Place the chopped bittersweet chocolate in a medium heatproof bowl.

In a large glass measuring cup or another medium bowl, microwave the heavy whipping cream until steaming, 45 seconds to 1 minute.

Immediately pour the warm cream over the chopped chocolate.

Allow to sit for 1 minute before whisking until smooth. If the chocolate is not fully melted, microwave the mixture at 50% power at 15-second intervals, stirring until smooth.

9. Glaze the Eclairs: Set a wire rack over a baking sheet (to catch any drips).

Dip the tops of the filled eclairs into the chocolate glaze. Only submerging the tops.

Let any excess chocolate drip off.

Set the dipped eclairs onto the prepared wire rack.

10. Set and Serve: Allow the chocolate glaze to set before enjoying, about 20 minutes.

Store the eclairs in an airtight container in the refrigerator for up to 3 days. They are best enjoyed the day they are made. Enjoy your beautiful and delicious Chocolate Eclairs!