Preheat the oven to 350°F and line a 9×9-inch baking pan with parchment paper. Grease the parchment paper with a light brushing of olive oil or melted vegan butter, or with cooking spray.

In a medium bowl, prepare the cinnamon streusel. Whisk together the flour, brown sugar, cinnamon, and salt. Stir in the olive oil until the mixture resembles a wet sand-like texture. Set aside.

In another medium bowl, prepare the pumpkin coffee cake batter. Whisk together the flour, cane sugar, pumpkin pie spice, baking powder, baking soda, and salt. Add in the pumpkin puree, milk, olive oil, and vanilla and whisk until just combined. It's okay for the batter to have some lumps, as long as they aren't lumps of dry ingredients. Be careful not to over mix to prevent the cake from turning out dense.

Next, assemble the coffee cake. Pour about half of the cake batter into the prepared pan and spread to the edges. Sprinkle about half of the cinnamon streusel evenly on top. Repeat with the remaining cake batter and streusel.

Bake the cake for 55-60 minutes or until a toothpick inserted into the center of the cake comes out clean. Allow to cool in the pan for 15 minutes.

When ready to serve, it’s best served slightly warm. Slice into 9 or 12 squares.

Prepare the vanilla icing, if using. Whisk together the powdered sugar, milk, and vanilla, starting with less milk and adding a tiny bit more if needed to reach a drippy consistency. If it gets too runny, add some more powdered sugar to thicken it back up. Drizzle the icing on top of each slice. Enjoy!