Preheat oven to 350F. Line an 8-in square pan with parchment paper and set aside. In a medium bowl, beat butter and sugar until completely creamy. Fold in vanilla and flour until a soft dough forms.
Pat dough evenly into bottom of prepared pan and prick all over with a fork. Bake shortbread at 350F 10-12 minutes until golden-brown. Cool shortbread completely on a wire cooling rack, then crumble into bite-sized pieces. Set aside.
Blueberry Sauce
In a medium saucepan, whisk cornstarch, water, and lemon juice until smooth. Add blueberries and sugar to pan and bring to a low simmer over medium-high heat, stirring occasionally until blueberries are broken down and sauce is thickened. Cool sauce completely.
Frozen Yogurt
In a medium bowl, whisk frozen yogurt, condensed milk, honey, and vanilla until smooth. Very gently fold in whipped cream.
In a loaf pan or a long freezer-safe container, spread 1/3 of yogurt mixture and top with swirls of 1/4 cup of lemon curd and 1/4 cup blueberry sauce, followed with 1/3 of shortbread crumbles. Repeat layers two more times
Cover frozen yogurt with plastic wrap and freeze until solid and firm, about 4-6 hours. If you let the frozen yogurt freeze longer than 6 hours, I recommend letting it sit out at room temperature 10-15 minutes to soften a bit before scooping. Enjoy!
Notes
**As an alternative to premade lemon curd, you can make your own homemade version using this recipe.