Set your oven to 350°F / 175°C. Line your baking pan with parchment paper for easy removal later.

Melt the butter, then whisk in the sugar until smooth. Add the eggs and vanilla and mix well.

Stir in the flour, cocoa powder, and salt until just combined.

Spread the brownie batter evenly into your prepared pan.

In another bowl, whisk together the pumpkin puree, egg, sugar, vanilla, spices, and cornstarch until smooth.

Pour this pumpkin mixture over the brownie layer and spread it out evenly.

Mix together the flour, brown sugar, and spices.

Cut in the cold butter using your fingers or a fork until the mixture looks like damp crumbs.

Sprinkle this streusel evenly over the pumpkin layer.

Bake for 35–40 minutes, until the center is set and the streusel turns golden brown.

Let the brownies cool completely before slicing — if you can wait that long!