Martha Stewart's Crispy Chocolate-Marshmallow Treats

From the guru's website. Sounds easy, delish and great for parties. Haven't made, am posting for safe keeping.

• Ready In: 20 mins
• Serves: 4
• Yields: 16 pieces

Ingredients

• 6  tablespoons unsalted butter, plus more for pan
• 10  ounces mini marshmallows
• 1⁄4 cup  unsweetened  Dutch-processed cocoa powder (spooned and leveled)
• 6  cups  crisp rice cereal
• 2  ounces bittersweet chocolate, melted

Directions

1. Butter an 8-inch square baking pan. Line bottom and two sides with parchment paper, leaving a 2-inch overhang on both sides. Butter paper; set pan aside.
2. In a large saucepan, combine butter, marshmallows, and cocoa. Cook over medium, stirring frequently, until melted, about 6 minutes; stir in rice cereal. Press rice mixture into prepared pan; drizzle with melted chocolate.
3. Let cool to room temperature; cut into 16 bars.
4. (To store, keep in an airtight container at room temperature, up to 5 days.).