1. **Preheat the oven** to 350°F (175°C) and line a 10×15-inch jelly roll pan with parchment paper. Lightly grease it.
2. **Prepare the cake batter**: In a bowl, whisk together flour, cocoa powder, baking powder, and salt. In a separate bowl, beat the eggs and sugar until pale and fluffy, about 5 minutes. Add water and vanilla. Gradually mix in the dry ingredients.
3. **Bake the cake**: Spread the batter evenly in the prepared pan. Bake for 12-14 minutes, or until the cake springs back when lightly touched.
4. **Roll the cake**: While still warm, turn the cake onto a towel dusted with powdered sugar. Roll the cake up with the towel, starting from the short end. Let it cool completely.
5. **Make the filling**: Whip heavy cream, powdered sugar, and vanilla until stiff peaks form. If desired, fold in chocolate chips for added texture.
6. **Assemble**: Unroll the cake and spread the whipped cream evenly. Gently roll it back up.
7. **Optional glaze**: Heat heavy cream and chocolate chips together, stirring until smooth. Pour over the rolled cake for an extra chocolatey touch!
8. **Chill** for 1 hour before slicing and serving.
