In a small saucepan over medium-high heat the granulated sugar and lemon juice together. Stir until the sugar is completely dissolved then set aside to cool.
In the bowl of a stand mixer whip together the Dream Whip [The box contains 2 envelopes use both] and 2 cups of cold whole milk. Whip for 5 minutes or until soft peaks form.
Add both packages of lemon pudding and the remaining 1 cup of whole milk. Whip for 2-3 minutes until thickened.
To assemble, Divide the cubed cake in half. Begin with a layer of cubed cake on the bottom of the trifle bowl. Brush with 1/2 of the lemon syrup. Add a layer of lemon cream and 1/2 of the whipped topping. Repeat with cake, brush with lemon syrup, lemon cream ending with whipped topping.
Sprinkle the top with grated white chocolate and garnish with lemon slice and fresh mint if desired.
Chill thoroughly for at least 4 hours prior to serving.