Nothing says summer quite like a tart key lime pie. This mousse is every bit as refreshing, with a fluffy texture and a crispy oat crumble we could eat on its own.
FOR THE CRUMBLE
4 graham crackers
3/4 c. rolled oats
1/3 c. packed light brown sugar
3 tbsp. all-purpose flour
6 tbsp. cold butter, cubed
FOR THE MOUSSE
1 1/2 c. heavy cream
1/4 c. powdered sugar
1 c. sweetened condensed milk
1/3 c. freshly squeezed key lime juice
1 tsp. pure vanilla extract
Green food coloring (optional)
Key lime wedges, for garnish
Preheat oven to 350°. In a food processor, pulse graham crackers into fine crumbs. In a medium bowl, combine crushed graham crackers, oats, brown sugar, and flour. Add butter and use your hands to cut into mixture until pea-sized and mixture starts to hold together. Spread mixture into an even layer on a baking sheet. Bake until golden and crisp, about 20 minutes, stirring halfway through. Let cool.
Make mousse: In a large bowl, using a hand mixer (or in the bowl of a stand mixer fitted with the whisk attachment), beat cream and powdered sugar into stiff peaks. Remove about 1 cup of whipped cream to reserve for topping.
In a medium bowl, combine condensed milk, lime juice, vanilla, and a small drop of food coloring, if using. Add to bowl of whipped cream. Gently fold in until just combined.
Assemble: Add about ¼ cup of crumble to the bottom of 4 glasses. Top with two large spoonfuls of mousse, then repeat with another layer of crumble and mousse.
Place reserved whipped cream in a piping bag fitted with a large closed star tip, and pipe onto mousse. Top with any remaining crumble and a lime wedge in each glass.
Keep refrigerated until ready to serve.