Preheat oven to 350°. Spray 12 (2-inch-wide) wells of a mini muffin pan with cooking spray.
In a large bowl, whisk egg whites until foamy. Add coconut and sugar, stirring until well combined and mixture holds when pressed together. Place 1 heaping tablespoon coconut mixture in each prepared well. Using fingertips, press mixture into a ¼-inch-thick shell.
Bake until golden brown, approximately 15 minutes. Remove from oven. Using the back of a levered 1-teaspoon measuring scoop, press down center indentations again. Carefully remove coconut shells from muffin pan. Let cool on a wire rack for 15 minutes.
Place chocolate in a medium heatproof bowl. In a medium saucepan, bring cream, corn syrup, and salt to a simmer together, stirring frequently. Pour hot cream mixture over chocolate. Let stand for 2 minutes. Add vanilla extract, stirring until chocolate mixture is smooth and well combined. Transfer chocolate mixture to a small piping bag. Cut a ¼-inch hole in tip. Pipe approximately 1 teaspoon chocolate mixture into each coconut shell. Let cool for 10 minutes.
Place Sweetened Whipped Cream in a piping bag fitted with a medium open star tip (Ateco #822). Pipe cream rosettes onto tartlets. Serve immediately.
Notes
Make-Ahead Tip: Tartlets can be made a day ahead, cooled, placed in an airtight container, and refrigerated. Let come to room temperature, and pipe with cream just before serving.
Recipe by TeaTime Magazine at https://teatimemagazine.com/chocolate-macaroon-tartlets/