For Eclairs:
Preheat oven to 425°F.
Measure all ingredients and set aside. Line a baking sheet with parchment paper.
In a saucepan, mix water, butter, sugar, and salt and bring to a boil. Remove from heat and stir in flour.
Return to heat and stir for 1-2 minutes until the dough forms a smooth ball. Transfer to a stand mixer and let rest for 5 minutes.
Add chocolate extract, if using. Beat in eggs one at a time until the mixture is smooth and glossy.
Spoon the dough into a pastry bag and pipe into 1-inch by 4-inch strips on the prepared baking sheet.
Bake at 425°F for 5 minutes, then reduce heat to 350°F and bake for another 30 minutes. Turn off the oven and let eclairs rest inside for 10 minutes.
For Chocolate Whipped Cream:
In a stand mixer with a whisk attachment, whip all ingredients on medium speed until light and fluffy.
For Chocolate Ganache:
In a microwave-safe bowl, heat chocolate and cream on high for 30 seconds. Stir until smooth. Repeat in 15-second intervals if needed.
To Assemble:
Cut eclairs in half. Dip the top half in ganache and let rest chocolate side up.
Fill the bottom half with chocolate whipped cream and cap with the chocolate-dipped top.