In a medium saucepan cook and stir unsweetened chocolate and butter over low heat until melted and smooth.

Remove from heat; cool slightly.

Preheat oven to 350 degrees. Line a 13x9x2 inch baking pan with foil.Grease foil.

Stir sugar into chocolate mixture. Add eggs, one at a time, beating with a wooden spoon after each addition. In a small bowl stir together the flour and baking soda. Add flour mixture to the chocolate mixture.

Stir in semisweet chocolate morsels.

Pour batter into prepared pan and spread evenly.

Bake for 20-25 minutes or until almost set.

When brownies are almost finished transfer dulce de leche to a microwave-safe bowl. Microwave on high for one minute or until soft, stirring once.

Remove brownies from oven and set pan on a wired rack.

Immediately spoon marshmallow cream in mounds on top of brownies.

Drop spoonfuls of dulce de leche between mounds of marshmallow cream.

Let stand a few minutes.

Using a a table knife, swirl marshmallow cream and dulce de leche around to marble. Sprinkle with pecans.

Let set for approximately 20 minutes.

Lift foil from pan and cut brownies.