If you’re looking for a quick-to-assemble dessert, look no further than this maple-walnut icebox cake. The syrup and extract add just the right amount of maple sweetness to the whipped cream frosting, while graham crackers magically turn soft and cake-like in the fridge. Coat the edge with a crunchy layer of toasted nuts for a crowd-pleasing treat.
Add the walnuts to a large nonstick skillet over medium heat. Cook, stirring often, until toasted and fragrant, about 5 minutes. Transfer to a cutting board to cool. Once cool, finely chop and store in an airtight container until ready to use.
Meanwhile, beat the mascarpone, sugar, maple syrup, maple extract, vanilla and salt together in a stand mixer fitted with the whisk attachment on medium-low speed until smooth. With the machine running, slowly add the heavy cream, then increase the speed to medium-high. Continue to beat until fluffy and thick enough to hold stiff peaks, about 2 minutes.
Line the bottom of an 8-inch springform cake pan with a single layer of graham crackers, breaking up some of them to fill in any gaps. You will need 2 to 3 graham crackers per layer. Spread about 3/4 cup of the maple whipped cream evenly over the top of the crackers, making sure to go all the way to the edges. Repeat until all the crackers and whipped cream have been used, ending with a layer of whipped cream. Use a small offset spatula to create a decorative swirl on top.
Cover the pan loosely with plastic wrap and refrigerate until the cookies have softened and the cake is chilled through, at least 8 hours and up to 12 hours.
Gently run a small offset spatula or paring knife around the edge of the cake, then unlock the pan and remove the outer ring. Coat the sides of the cake with the chopped walnuts. Slice into wedges and serve.