Grease a 9 x 13 pan and set aside.

Zest the orange.

In a large separate bowl whisk together the flour, oatmeal, sugar, cinnamon, orange zest.

Knead the butter into the dry ingredients until it forms streusel crumbs.

Press half the streusel mixture into the prepared pan.

Place the chocolate chips in a heatproof bowl. Heat espresso until boiling and pour over the chocolate chips. Stir to smooth out the mixture.

Separate the eggs.

Beat the egg whites and salt until stiff peaks form. Sprinkle the sugar over the egg whites.

Add the egg yolks, almond butter, nutmeg to the espresso chocolate. Mix thoroughly.

Fold in the sugared egg whites, then fold in the buckwheat flour.

Assemble the cake:

Preheat the oven to 350 degrees F.

Spread the mixture out on top of the streusel in the pan.

Distribute the rest of the streusel on top.

Remove from oven and let cool for 10 minutes before drizzling the syrup over the top.

Place the remaining 1/4 cup of espresso, powdered sugar, and coffee liquor into a saucepan and cook, stirring until dissolved.

Bring to a boil, then remove from heat.

Drizzle over the cake.