Preheat an oven to 400°F. Spoon pumpkin on to a rimmed baking sheet. Smooth out into an even, thin layer, and bake for 15 minutes. Let cool, then measure out 1 cup (225 grams) puree.
Reduce heat to 325°F. Butter and lightly flour a 9-inch loaf pan.
In a large bowl, add flour, baking powder, baking soda, cinnamon, nutmeg and salt, whisking to combine. In a medium bowl, whisk together eggs, pumpkin puree, sugar and olive oil until smooth. Add the wet ingredients to the dry ingredients, stirring just until combined. Fold in the chocolate.
Pour the batter into the prepared loaf pan, and bake until the top is golden brown and a toothpick inserted into the middle of the cake comes out clean (75 to 80 minutes). Transfer to a cooling rack and cool for 20 minutes. Carefully remove the cake from the tin and let cool for an additional 20 minutes.
To make the glaze, add confectioners' sugar and water to a medium bowl, whisking until smooth. The consistency should be similar to honey - add more sugar or water as needed to achieve the right texture. Slowly drizzle in the olive oil, whisking constantly. The glaze should be thick but pourable.
To finish, drizzle the glaze over the cake, letting it run down the sides. Sprinkle the top evenly with toasted pepitas and cocao nibs. Let the glaze set completely before serving (about 1 hour).