Preheat oven to 350 degrees F.
In a small pan over low heat, melt the butter, yielding 1 cup. Use very low heat. You want to melt the butter but not discolor it.
In a medium size bowl, crumble the Oreo cookie crumb pie crust, setting aside 1/3 cup of crumbs in another container.
Combine 1/2 cup of melted butter with the larger portion of cookie crumbs and spread evenly to cover the bottom of an ungreased 9"x13" glass baking dish, pressing down to form a thin layer.
In a medium bowl, mix the walnut brownie mix according to directions on the package, using 1/4 cup of melted butter instead of oil. Add approximately 1/3 cup of miniature marshmallows. Mix by hand until well blended; about 50 strokes.
In a large mixing bowl, mix the milk chocolate brownie mix according to directions on the package, using melted butter instead of oil. Add pecans. Add approximately 1/3 cup of miniature marshmallows and mix by hand until well blended; about 50 strokes.
Empty the walnut brownie mix into the bowl containing the milk chocolate brownie mix. Blend the two mixes together, but not too thoroughly; leaving it somewhat marbled, as if making a marble cake.
Pour the resulting mixture into the 9"x13" baking dish, spreading evenly over the layer of cookie crumbs.
Sprinkle reserved cookie crumbs randomly over the top of the mixture, leaving the mix below visible. The object is to give the illusion of black topsoil scattered over the lighter river mud. If the optional Delta Mud Glaze below is used, save this step for last. See glaze instructions below.*
Bake for approximately 35 minutes. Brownies are done when a toothpick inserted approximately 2 inches from the edge comes out almost clean (marshmallow may leave traces on the toothpick).
Remove from the oven and place on a cooling rack until completely cool.
Cover and leave the brownie intact (uncut) until served to preserve the moistness of the brownie.
A mixture of textures and color in the brownie's interior is normal and desired to simulate Mississippi mud. The visual effect is part of the Mississippi Mud experience.
OPTIONAL DELTA MUD GLAZE
*NOTE: If glaze is used, save the reserved Oreo cookie crumbs for last and sprinkle over the glaze
For a more decadent Mississippi Delta type mud, make the Optional Delta Mud Glaze after the brownies have cooled as follows:
Combine cocoa powder and butter in a sauce pan over low heat, stirring to blend the cocoa and butter. Add powdered sugar, a little at a time, blending thoroughly after each addition, until well blended. Stir in 1 teaspoon at a time of hot water until desired consistency is achieved. Stir in vanilla extract or rum flavoring last.
Immediately pour glaze over the cooled brownies and spread as evenly as possible.
Sprinkle reserved Oreo cookie crumbs randomly over the glaze, but do not completely cover the glaze. As stated earlier, this is primarily a visual effect. . Allow to cool before serving.
Makes 12 brownies approximately 3-inches square.
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