ABOUT 3 HOURS BEFORE SERVING OR EARLY IN DAY:
Line 9x9 inch baking pan with foil; press out wrinkles so chocolate box will come off foil smoothly.
In heavy 1-quart saucepan over low heat, heat semi-sweet chocolate squares with shortening until melted and smooth, stirring frequently. Pour melted chocolate mixture into foil-lined pan; swirl chocolate around sides and bottom of pan to cover entire inside of pan, keeping edges as even as possible. Refrigerate 1 minute, then swirl chocolate mixture around inside of pan, a second time, to reinforce sides of chocolate box. Refrigerate until chocolate is firm, about 30 minutes.
Meanwhile, prepare filling: In large bowl, with mixer at medium speed, beat cream cheese and butter until smooth (do not use butter or filling will be too soft to cut). Add confectioners' sugar, cocoa, milk, and vanilla extract; beat until light and fluffy.
In small bowl, with mixer at medium speed, beat 1 1/2 cups heavy cream until stiff; with rubber spatula, fold into cream cheese mixture.
Remove foil-lined chocolate box from pan; gently peel foil from sides and bottom of chocolate box. Place chocolate box on platter. Spread cream cheese mixture evenly in chocolate box. Refrigerate until filling is well chilled and firm, about 2 hours.
In small bowl, with mixer at medium speed, beat remaining 1/2 cup heavy or whipping cream until stiff peaks form. Spoon whipped cream into decorating bag with large rosette tube. Pipe whipped cream in 1-inch wide border on filling around chocolate box. Cut larger strawberries in half and arrange over entire top of cream cheese filling. Garnish top of dessert with mint leaves.
Cut remaining strawberries into slices to serve with dessert. Makes 9 servings. About 525 calories per serving.
