Preheat oven to 350°F. Line an 8×8" pan with parchment paper.

Start by making the streusel. In a medium mixing bowl, whisk together the flour, pecans, sugars, and salt. Add the cold butter. Use your fingertips to pinch the butter into the dough until well distributed and mixture is sand-like. Store in fridge while preparing the cake.

In a medium mixing bowl, whisk together the flour, baking powder, pumpkin spice, and salt. Whisk together non-dairy milk and lemon juice in a liquid measuring cup. Set aside.

In a separate larger mixing bowl, use a handheld mixer or stand mixer to beat together the butter and sugars until light and fluffy then mix in the pumpkin puree and vanilla. With the mixer on low speed, add a third of the milk and a third of the flour to the butter mixture at a time. Mix until all the milk and flour is incorporated and a smooth batter forms (make sure not to overmix or the cake will be too dense). Fold in chocolate chips. 

To make the cinnamon filling, in a separate small bowl pinch together the softened butter, flour, sugar, cinnamon, and pumpkin spice until soft crumbs form.

Pour half the cake batter into the prepared baking dish. Sprinkle filling over the top, then pour over remaining cake batter. Sprinkle over streusel topping and lightly press so it sticks.

Bake for 50-55 minutes or until top is golden brown and toothpick inserted comes out clean or with a few moist crumbs. While cake is cooling, whisk together all icing ingredients until creamy. Let cool for at least 30 minutes before slicing, serving, and topping with icing. Enjoy!