Cut loaf cake into half-inch cubes and place on the bottom of 12 four-ounce cups.

In a four-quart pot on medium heat, place berries, sugar, and lemon juice. Stir until sugar is dissolved and mixture begins to boil. Lower heat to a simmer and let mixture cook for approximately 30 minutes until the sauce thickens and coats the back of a spoon and berries are soft. Allow to cool completely before continuing.

Separate mixture into two. Spoon half the mixture into prepared mousse cups, approximately one tablespoon per cup. Blend the other half with an immersion blender until smooth.

In the bowl of an electric mixer, beat whipped topping until soft peaks form. Slowly add confectioners’ sugar and beat until stiff peaks form. Add lemon zest and beat for a couple seconds longer. Gently fold the blended blueberry mixture into the whipped cream and spoon or pipe into the mousse cups. Top each mousse cup with a few fresh or frozen berries.