Preheat oven to 350°F (175°C). In a bowl, mix graham cracker crumbs, sugar, cinnamon, and melted butter until combined. Press the mixture into a 9-inch tart pan. Bake for 8-10 minutes, then let cool completely.

In a small bowl, sprinkle gelatin over cold water and let it sit for 5 minutes. Microwave for 10 seconds until dissolved.

Mash bananas and mix with lemon juice, sugar, and vanilla extract. In a separate bowl, whip the heavy cream until stiff peaks form.

Stir the dissolved gelatin into the banana mixture. Gently fold in the whipped cream until smooth. Pour the mousse into the cooled crust and smooth the top.

Refrigerate for at least 4 hours or until set. Before serving, top with sliced bananas, whipped cream, and optional chocolate shavings or caramel drizzle.