Raspberry Mousse Pie

Lightly coat a 9-inch square metal baking pan with cooking spray and line with parchment paper, leaving a 2-inch overhang on all sides. Arrange graham crackers in an even layer in pan, breaking them to fit as necessary. Place lemon juice in a small bowl and sprinkle with gelatin. Let sit until gelatin softens, 3 minutes. In a blender, puree 2 cups raspberries until smooth, scraping down bowl as needed. Pour through a fine-mesh sieve into a measuring cup, pressing on solids (you should have about 1 cup of puree); discard solids.

In a small saucepan, combine raspberry puree and 1/2 cup sugar over medium. Cook until bubbles form at edge. Add gelatin mixture and cook, stirring constantly, just until gelatin dissolves, about 1 minute. Transfer mixture to a small bowl and let cool to room temperature, 20 minutes. In a large bowl, using an electric mixer, beat cream and 2 tablespoons sugar on medium-high until firm peaks form, about 4 minutes. With a rubber spatula, gently fold in raspberry puree mixture until combined. Pour over graham crackers. Smooth top with an offset spatula and arrange 3 cups raspberries on top. Refrigerate until set, about 2 hours (or up to overnight).

Using parchment, gently lift pie out of pan and place on a serving plate. Peel away parchment from sides of pie; trim excess paper with scissors or a sharp knife. Cut into 12 pieces to serve.