A chilled no-bake cake with cocoa biscuit layers, Nutella, creamy mascarpone filling, and tangy sour cherries.
Frozen sour cherries work well. Fresh or drained jarred sour cherries can also be used. Add more sugar if you prefer a sweeter cherry layer.
Mix the cornstarch with cold water before adding it to the cherries. The filling thickens very quickly, so watch it closely and cool it completely before assembling.
Do not overwhip the heavy cream. Once soft peaks form, add the mascarpone and mix only until thick and creamy.
Dip the biscuit sandwiches in milk only briefly so they do not fall apart. They will soften further as they absorb moisture from the filling while the cake chills.