How to make...Brownies.

Ingredients

• Non-stick cooking spray (or butter) for greasing pan
• 5 ounces 70% bittersweet chocolate, finely chopped
• 8 tablespoons (4 ounces) unsalted butter
• 3/4 cup (3 3/4 ounces) all-purpose flour
• 2 tablespoons cocoa powder
• 1 cup (7 ounces) granulated sugar
• 2 large eggs
• 1 large yolk
• 1/4 teaspoon plus 1/8 teaspoon salt
• 1 1/2 teaspoons pure vanilla extract
• 1/2 cup walnuts, chopped

Procedures

1. 1
   Adjust oven rack to medium position and preheat oven to 350°F. Spray 8- by 8-inch baking pan with non-stick pan spray. In heatproof bowl over pan of barely simmering water, heat chocolate and butter until just melted, stirring occasionally. Remove from heat and let cool slightly.
2. 2
   Sift flour and cocoa into medium bowl; set aside. In large bowl, whisk sugar with eggs, yolk, salt, and vanilla until light, about 30 seconds. whisk in chocolate mixture. Using wooden spoon, stir in chocolate mixture until combined. Stir in flour mixture until combined.
3. 3
   Pour batter into prepared pan and smooth top. Evenly sprinkle walnuts over top. Bake until just set and toothpick inserted into center comes out with moist crumbs about 30 minutes. Let cool on wire rack about 45 minutes before cutting into squares.

How to make...Oreo cake.

Ingredients

• For the Cake:
• 3/4 cup all-purpose flour
• 1/4 cup cocoa powder
• 1/2 plus 1/8 teaspoon baking soda
• 1/8 teaspoon salt
• 1/2 cup plus 2 tablespoons granulated sugar
• 1/2 cup plus 2 tablespoons sour cream
• 1/3 cup vegetable oil
• 1 large egg
• 1/2 teaspoon pure vanilla extract
•  
• For the Oreo whipped cream:
• 50 Oreo cookies
• 4 1/2 cups heavy cream
• 2 tablespoons granulated sugar
• 1 tablespoon pure vanilla extract

Procedures

1. 1
   Make cake: Adjust oven rack to middle position and preheat oven to 350°. Line bottom of a 9-inch cake pan with parchment paper and lightly coat the inside with non-stick pan spray. Sift flour, cocoa, baking soda, and salt into large bowl; set aside. In medium bowl, whisk sugar, sour cream, oil, eggs, and vanilla until smooth.
2. 2
   Whisk wet ingredients into dry ingredients until smooth. Pour batter into pan and bake until cake is just firm and toothpick inserted into center comes out with moist crumbs, 20 to 25 minutes. Let cake cool in pan for 15 minutes, then remove from pan to completely cool on wire rack, about 1 hour.
3. 3
   Carefully cut 6 Oreo cookies in half; set aside. Chop remaining cookies into 1/4s; set aside.
4. 4
   To Assemble Cake: Whip 2 cups of cream on medium-high speed to soft peak, spoon into large bowl and refrigerate. In same mixer bowl, whip remaining 2 1/2 cups cream, sugar, and vanilla to soft peak. Fold into already whipped cream.
5. 5
   Place about 1 cup whipped cream in bowl and refrigerate until ready to decorate cake. Fold chopped Oreos into remaining whipped cream.
6. 6
   Slice cake in half horizontally to create 2 layers. Place bottom layer on serving plate. Spread about 1/3 of Oreo whipped cream onto cake. Top with second cake layer and use remaining Oreo whipped cream to frost top and sides of cake. Chill in refrigerator for about 2 hours to allow cookies to soften.
7. 7
   Place reserved whipped cream in pastry bag fitted with star tip (re-whisk if necessary). Pipe 12 whipped cream rosettes around perimeter of cake and garnish with reserved Oreo cookie halves. Serve.

   
   

   (Credit to @antararoy13)