Preheat the oven to 350°F and line a baking sheet with parchment paper.
Make the streusel topping by mixing the butter, coconut sugar, oat flour, cinnamon, salt, and optional oats with a fork until crumbly. Chill while you prepare the dough.
In a large bowl, cream the butter, coconut sugar, and brown sugar until smooth. Add the maple syrup, egg, egg yolk, vanilla extract, and espresso powder and mix until combined.
Add the cinnamon, ginger, cardamom, nutmeg, allspice, and black pepper and mix lightly.
Fold in the all purpose flour, oat flour, baking soda, and salt until just combined. Do not overmix.
Scoop the dough into about 1½ tablespoon portions and place on the prepared baking sheet. Sprinkle each cookie with streusel topping.
Bake for 9 to 11 minutes, until the cookies are soft and just set. Let cool completely.
Whisk together the Greek yogurt, maple syrup, vanilla extract, and sea salt. Drizzle the glaze over the cooled cookies.
