Preheat your oven to 350°F. In a bowl, combine the cookie mix, melted butter, egg, and flour until the mixture comes together. Press this mixture firmly and evenly into a 9x13 inch baking dish, making sure to fill all corners and create an even layer. Bake for 10-12 minutes until the edges are lightly golden but the center still looks slightly underbaked—it will continue to set as it cools. Remove from the oven and let cool to room temperature before proceeding to the next step.

While the crust cools, prepare the glaze. In a saucepan, mash 1 cup of the hulled and sliced strawberries with the sugar until the berries break down and release their juices. Add the cornstarch, flour, and water, stirring until smooth and well combined with no lumps. Bring the mixture to a boil over medium-high heat, stirring constantly to prevent sticking, and boil for 2 minutes until the mixture thickens and becomes translucent. Remove from heat, stir in the lemon juice, and let the glaze cool to room temperature—this prevents it from melting the cream cheese layer.

In a large bowl, beat the room-temperature cream cheese with an electric mixer until smooth and creamy—starting with room temperature cheese prevents lumps and creates a silkier texture. Add the vanilla extract and sifted powdered sugar, beating until light and fluffy, about 2-3 minutes. I like to sift the powdered sugar beforehand to avoid any grainy texture in the final filling.

Spread the cream cheese mixture from Step 3 evenly over the cooled crust from Step 1, creating an even layer that reaches the edges. Arrange the remaining 1 quart of hulled and sliced strawberries in a single layer over the cream cheese, placing them close together for full coverage. Pour the cooled strawberry glaze from Step 2 over the strawberries, spreading it gently to coat all the berries and fill in any gaps. Refrigerate for at least 2 hours until the glaze sets completely and the bars are chilled throughout before cutting and serving.