• Preheat oven to 350°F and lightly grease an 8x8" baking pan, or line with parchment so the cake can be easily lifted out of the pan.

Prepare the Streusel

• Prep the streusel ahead of time so it's ready to go. Mix together flour, brown sugar, cinnamon, nutmeg, and salt.
• Add in the softened butter and mix until the ingredients come together in a crumbly mixture. I like to use a fork or my hands for this. The mixture should be fairly crumbly but it should be fairly evenly-hydrated — meaning there shouldn't be a lot of dry flour in the mix. If there is, keep mixing to combine everything a bit more. Pop the mixture in the fridge until ready to use.

Make the Coffee Cake

• In a large mixing bowl, cream together softened butter and granulated sugar for 3-5 minutes. The mixture should go past the stage where it is crumbly, and become very fluffy, smooth, and light in color.
• Add the pumpkin purée into the mixture and beat until incorporated.
• To the same bowl, add flour, baking powder, salt, cinnamon, cloves, nutmeg, milk, and vanilla extract.
• Beat together until it is almost fully mixed, but there's still a bit of the dry mixture visible. At this point I like to swap to a rubber spatula to help ensure that I don't over-mix. Fold the batter until everything is just combined, and there is no more dry flour. The batter will be quite thick and fluffy.
• Transfer the batter to your prepared 8x8" pan and spread about half of it out in an even layer. (I like to use an offset spatula for this but a rubber spatula works fine too.)
• Take the streusel topping from the fridge and use your hands to crumble about half of it over the top of the batter in an even layer.
• Top the streusel with the remainder of the batter and spread it in another even layer. It can be a little tricky to spread the batter over the first layer of streusel. It can be helpful to dollop the batter around the pan first so you're not spreading it all out from one spot. Then gently spread.
• Add the remainder of the streusel topping to the top of the coffee cake.
• Bake in a preheated oven for 40-50 minutes — this can vary quite a bit oven-to-oven. If you gently shake the pan, the center should be completely set (not jiggly at all). A knife/toothpick inserted into the center should come out clean or with only a few moist crumbs. Lastly, the streusel topping should be crisp and not soggy — if it still looks wet, cook for an extra 5 minutes and check again.
• The cake will be a bit gummy if you cut into it right away. I recommend allowing it to cool in the pan for about 30 minutes before enjoying.

Make the Glaze (optional)

• If preferred, you can skip the glaze and simply dust the cake with powdered sugar once it has had a chance to fully cool. (The sugar will melt if the cake is too warm.)
• If making the glaze, whisk together all ingredients and drizzle over the cooled coffee cake.

Storing

• The streusel topping will lose some of its crisp if leftovers are stored in an airtight container. I recommend leaving it in the pan on the counter, and loosely tenting it with foil to help it stay crispy.