Preheat oven to 350°F Butter an 8-inch square pan.
Melt chocolate and butter in medium-sized heavy saucepan over low heat.
Remove from heat; cool slightly.
Stir in eggs, honey and vanilla.
Combine flour, baking powder and salt in small bowl.
Stir into chocolate mixture with walnuts.
Spread batter evenly in prepared pan.
Bake 20 to 25 minutes or just until center feels springy.
Cool in pan on wire rack.
Cut into 2-inch squares.