Prepare the cherry layer by combining fresh cherries, sugar, and lemon juice in a saucepan over medium heat. Bring to a simmer and cook for 5-7 minutes until cherries soften and release their juices. Remove from heat and cool completely. (Skip this step if using canned cherry pie filling.)
Cut the chocolate cake into 1-inch cubes. Don’t worry about making perfect squares – irregular shapes will add character to your trifle and soak up flavors beautifully.
Whip the cream in a large bowl using an electric mixer. When soft peaks begin to form, add powdered sugar and vanilla extract, then continue beating until firm peaks form. Be careful not to overwhip – you want it fluffy, not grainy.
Begin assembly by arranging half the chocolate cake pieces in the bottom of your trifle bowl, gently pressing to create an even layer.
Sprinkle the cake with half the cherry liqueur or juice, allowing it to soak in for a minute. The cake should be moistened but not swimming in liquid.
Spoon half the cherry mixture over the soaked cake, ensuring an even distribution and letting some cherries show along the edge of the bowl for visual appeal.
Pour half the custard over the cherries, spreading gently to the edges. Let it settle naturally into gaps between the cake pieces.
Add half the whipped cream on top of the custard, creating a smooth layer and again allowing some to show at the edges.
Sprinkle half the grated chocolate over the whipped cream layer, letting some fall against the glass for visual effect.
Repeat all layers once more: remaining cake, liqueur, cherries, custard, whipped cream, and finish with the remaining chocolate shavings.
Refrigerate the trifle for at least 4 hours, preferably overnight, to allow flavors to meld and layers to set properly.
Garnish before serving with fresh cherries and mint leaves if desired. Serve chilled, making sure to scoop deeply to capture all layers in each portion.