Streusel Coffee Cake

For the streusel: In the bowl of a stand mixer fitted with a paddle, combine the all-purpose and almond flours, granulated and brown sugars, cinnamon, and salt on low speed. Add the butter one piece at a time, until the mixture comes together but still quite crumbly. Set aside 1 ½ cups [188 g] of the streusel to use on the cake, then store the remaining streusel in an airtight container in the refrigerator for up to 1 week, or freeze in a freezer-safe bag for up to 1 month.

For the coffee cake: Adjust an oven rack to the middle position and preheat the oven to 350F [180C]. Grease a 9 by 13 in [23 by 33 cm] pan and line it with a parchment sling.

In a medium bowl or liquid measuring cup, whisk together the milk, egg whites, crème fraiche, and vanilla. In the bowl of a stand mixer fitted with a paddle, combine the flour, granulated sugar, baking powder, and salt. With the mixer running on low speed, add the butter one piece at a time, beating until the mixture resembles coarse sand. With the mixer still running on low speed, slowly add a little more than half of the wet ingredients. Increase the speed to medium and beat until the ingredients are incorporated, about 30 seconds. Lower the speed to low and add the rest of the wet ingredients, mixing until just combined. Increase the speed to medium and beat for 20 seconds (the batter may still look a little bumpy). Scrape down the sides and bottom of the bowl and use a spatula to mix the batter a few more times. Pour all but 1 tablespoon of the batter into the prepared pan and smooth the top.

For the cream cheese filling: In a small bowl, whisk together the cream cheese, granulated sugar, and the reserved 1 tablespoon of cake batter. Dollop the cream cheese filling over the cake and use a knife or an offset spatula to swirl it into the batter. Sprinkle the set aside streusel [1 ½ cups | 188 g] evenly over the top. Tap the pan gently on the counter twice to help get rid of any air bubbles. Bake for 28 to 50 minutes* (SEE NOTE), rotating the pan halfway through, until the cake is golden brown and a wooden skewer or toothpick inserted into the center comes out with a faint bit of crumbs. Transfer the cake in the pan to a wire rack and let cool for 5 minutes.

For the icing: While the cake is baking, in a medium bowl, whisk together the confectioners’ sugar, 2 tablespoons of the water, the melted butter, and vanilla until smooth. Add more water, 1 tablespoon at a time, to thin the icing to your preferred consistency. Pour half of the icing over the warm cake and let sit for 20 minutes, then pour the remaining icing over the cake and let sit while the cake finishes cooling. Remove the cake from the pan using the parchment sling. Cut into pieces and serve. Alternatively, the cake can be left in the pan and covered in plastic wrap, then stored in the refrigerator for up to 2 days.