Preheat oven to 350º F degrees. Grease and flour an 8-inch baking dish. Or line with foil, and spray with non-stick spray.
In a bowl combine melted chocolate with canola oil. Add sugar and eggs. Mix until well combined. Stir in flour, salt, and baking powder.
2 ounces unsweetened chocolate, 1/3 cup vegetable oil, 1 cup granulated sugar, 2 whole eggs, 3/4 cup all-purpose flour, 1/2 teaspoon salt, 1/2 teaspoon baking powder
Pour batter into prepared pan. Bake for 25-30 minutes, until a tester comes out mostly clean. Remove from oven and let brownies cool completely.
To prepare chocolate mousse, heat marshmallows, chocolate chips, and milk in a saucepan over low heat, stirring occasionally until melted. Remove from heat and cool completely.
3/4 cup mini marshmallows, 4 ounces semi sweet chocolate chips, 1/4 cup milk
Once chocolate is cooled, whip heavy cream until stiff peaks form. Slowly add in cooled chocolate until well combined and stiff peaks reform.
1 cup heavy cream
Spread over cooled brownies. Store in the refrigerator for 2 hours to set before serving.