Combine all ingredients for the cake in the bowl of a stand mixer and mix on medium speed for 30 seconds. Scrape the sides with a spatula and make sure everything is incorporated into the batter. Alternately, you can also just whisk ingredients together in a mixing bowl.
Line an 8x6 baking dish with parchment paper. Using a spatula, spread batter evenly into baking dish.
Place cake in the oven and allow to cook for 15 minutes.
While cake is baking, combine ingredients for crumb topping in the bowl of the stand mixer. Mix until everything is incorporated and it starts to form clumps. Again, you could alternately just use a whisk and mixing bowl to combine ingredients depending on preference.
Remove cake from the oven and add the crumb topping. You won't want to spread it evenly, just dollop and crumble pieces on to the top to get a classic crumb cake look. Lightly press down on the crumb to help it adhere to the cake.
Place the cake bake in the oven for another 15 minutes or until the crumb browns.
Whisk together the ingredients for the icing in a small bowl.
Remove from the oven and allow to cool in the fridge. Once cake has entirely cooled and set properly, drizzle with icing immediately before serving. Slice and serve.
Store in the fridge for 4-5 days in an airtight container.