To make Frosted Strawberries: Place strawberries in colander, and spray with lukewarm water. Gently shake colander to remove excess water. Stem, then cut berries widthwise into 1/4-inch slices.
Place berries in medium-sized, noncorrosive bowl. Sprinkle sugar over berries, then toss gently to combine. Divide strawberries equally among 8- to 10-ounce glasses or cups for presentation. Set aside at room temperature.
To make Cocoa Yogurt Mousse: In sifter, combine confectioners’ sugar and cocoa powder. Sift mixture onto large piece of parchment paper, and set aside. Place heavy cream in bowl, and use electric mixer fitted with balloon whip.
Turn mixer on low speed while gradually adding dry ingredients. Mix until incorporated, about 1 minute. Use rubber spatula to scrape down sides of bowl. Whisk on medium speed for 5 seconds. Remove bowl from mixer.
Add yogurt, and fold ingredients together with rubber spatula until thoroughly combined. Immediately spoon yogurt mousse onto strawberries in each glass. Serve immediately, or cover with plastic wrap and refrigerate for up to 24 hours before serving.