In a large mixing bowl, mix almond paste and butter until fully combined.
Mix in eggs, brown sugar, and molasses until smooth.
In a separate mixing bowl, whisk together flour, cinnamon, ginger, clove, cardamom, salt, and baking powder.
Alternately add dry ingredients and oatmeal stout to the almond paste mixture, mixing until just combined.
Transfer batter to a greased one pound loaf pan.
Bake for 60-70 minutes or until a cake tester inserted into the center comes out dry. Expect the top of the loaf to crack a little bit; this is totally normal.
Cool slightly and turn out onto a cooling rack.
Glaze Instructions
Add milk to powdered sugar a little bit at a time until you have a runny but not completely liquid glaze.
Drizzle over cooled gingerbread.
Slice and serve.
Notes
If you want to tone down the spice level, you can use a mild molasses and/or use smaller amounts of the cinnamon, ginger, clove, and cardamom.