MAKE THE STREUSEL:

Place the brown sugar, cinnamon, salt and flour in a bowl and whisk to combine.  Add the cubed butter and press between your fingers until it resembles a wet sand.  Mix the chopped walnuts.  Set aside.

 

MAKE THE CAKE & ASSEMBLY:

In a small bowl, sift the flour, milk powder, baking powder, baking soda and salt.  Set aside. In a stand mixer fitted with a paddle, cream butter and sugar until light, about 5 minutes.  Add eggs one at a time making sure to mix well with each addition until it’s light and somewhat smooth.  Add the vanilla extract and sour cream.  Mix until light and smooth. Add the flour mixture and beat until flour is well incorporated with the wet mixture and there’s no lumps remain.  Scrape the sides and bottom and mix for a few seconds. Pour half of the batter into the prepared pan and smooth out the batter.  Add ¾ cup of the streusel mixture spreading all around the pan.  Add the remaining half of the dough and spread evenly and smooth the top.  Finish with the remaining streusel on top and press slightly into the dough. Bake and let cool on a wire rack for at least 30 minutes before removing from the pan.  This will ensure the layers are stable.

 

FOR THE GLAZE:

While the cake is cooling, whisk together the confectioners’ sugar and maple syrup until smooth.  If the mixture is too thick, add a few drop of water to loosen.  Drizzle on top of the cake once the cake is at room temperature to prevent the glaze from melting on top.