In a medium bowl, whisk together flour, cocoa powder, and baking soda. Set aside.
In a large mixing bowl, beat softened butter until creamy. Add brown sugar and 1 cup white sugar gradually, beating until fluffy.
Mix in eggs one at a time, then stir in vanilla.
Gradually add the dry ingredients to the butter mixture, mixing just until combined.
Stir in 1/2 cup chopped walnuts. Cover the dough and chill for at least 2 hours.
Preheat oven to 375°F (190°C). Grease or line two baking sheets.
In a small bowl, combine remaining walnuts with 1 tablespoon sugar.
Divide chilled dough into four portions, working with one portion at a time. Keep the rest refrigerated.
For each portion, divide into 12 pieces. Flatten slightly, wrap around a caramel candy, and roll into a ball.
Dip the top of each ball into the walnut-sugar mixture, placing them 2 inches apart on prepared baking sheets.
Bake for 8 minutes, or until set but still soft in the center.
Cool on baking sheets for 3–4 minutes before transferring to a wire rack.