Preheat oven to 425°. Lightly grease baking sheets or line with parchment paper. Measure flour and set aside.

Bring butter, sugar, salt, and 3/4 cup water to a boil in a 3-qt. saucepan over medium-high heat, stirring occasionally. Immediately remove from heat, and quickly stir in flour mixture all at once. Return to heat and stir with a wooden spoon for 1 to 2 minutes, or until dough is smooth and forms a ball. (Don't short-change this step or your dough may be too soft to pipe.) Transfer dough to the bowl of an electric mixer, and let cool 5 minutes.

Add 3 eggs, 1 at a time, beating until mixture is smooth and glossy. Spoon dough into a pastry bag fitted with a 5/8-inch plain tip. Pipe dough onto prepared pans into 1 1/2-inch rounds (1 1/2 inches high). Smooth out peaks and round tops with a moistened finger.

Whisk together remaining 1 egg and 1 tsp. water. Brush tops of dough with egg mixture.

Bake at 425° for 5 minutes; reduce oven temperature to 375°, and bake 30 minutes or until puffy and golden brown. Turn oven off; let shells stand in closed oven 10 minutes. Remove from baking sheets to wire racks, and cool completely.

Place cold water in small bowl and sprinkle gelatin over it. Let sit for 5 minutes. While it's sitting, place heavy cream, powdered sugar, and vanilla in the bowl of a stand mixer with the whisk attachment or in a mixing bowl if using an electric beater. Once gelatin is set, place bowl in microwave and heat until gelatin turns to liquid, about 5-10 seconds.

Turn mixer on to start beating cream. Let it run for about 1 minute and then with the mixer on high, very slowly pour the melted gelatin in, in a small steady stream.

Continue beating cream until you reach medium-stiff peaks. Place berries in a plastic bag and crush with hands into small pieces. Add to whipped cream and beat for an additional 30 seconds until well mixed.

When pastry shells are completely full, fill using one of the methods outlined in blog post.

Heat 1/2 cup heavy cream in microwave until steaming. Pour over chocolate in a heat safe bowl and let sit for 2-3 minutes. Whisk to combine until completely smooth. Sauce will be thinner when hot and thicken as it cools. Drizzle over tops of filled cream puffs, or dunk in bowl.