Step 1: Preheat your oven to 350°F (175°C) and grease a 9×5 inch loaf pan.
Step 2: In a small bowl, combine chopped dates and baking soda. Pour boiling water over them and let sit for 10 minutes until softened, then mash slightly with a fork.
Step 3: In a large bowl, cream together the softened butter and brown sugar until light and fluffy.
Step 4: Add the eggs one at a time, beating well after each, then stir in the vanilla extract.
Step 5: In a separate bowl, whisk together the flour, cardamom, cinnamon, and salt.
Step 6: Gradually add the dry ingredients to the butter mixture, alternating with the date mixture, beginning and ending with the dry ingredients.
Step 7: Fold in the walnuts if using. Pour the batter into the prepared pan.
Step 8: Bake for 45-55 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes before transferring to a wire rack.