01 - Whisk together lemon juice, lemon zest, sugar, and egg yolks in a small saucepan. Place over medium-low heat and cook, stirring constantly, until mixture thickens and coats the back of a spoon, approximately 5–7 minutes. Remove from heat and whisk in cubed butter until completely smooth. Transfer to a clean bowl and allow to cool to room temperature.
02 - Combine blueberries, sugar, and lemon juice in a small saucepan. Cook over medium heat, stirring occasionally, until blueberries burst and sauce slightly thickens, about 5–7 minutes. Remove from heat and allow to cool completely before using.
03 - In a chilled mixing bowl, beat heavy whipping cream with powdered sugar and vanilla extract using an electric mixer or hand whisk until soft peaks form. Do not overbeat.
04 - Gently fold the cooled lemon curd into the whipped cream using a rubber spatula. Continue folding until fully incorporated and mixture is smooth and uniform.
05 - Spoon a layer of blueberry compote into the bottom of each of 4 serving glasses. Top with lemon mousse mixture. Repeat layering if glasses allow, finishing with mousse on top.
06 - Refrigerate assembled mousses for at least 2 hours until fully set. Before serving, garnish with fresh blueberries, additional lemon zest, and fresh mint leaves if desired.