To make the cake: Preheat oven to 350 degrees F. Grease and flour an 8x8-inch baking dish. Set aside.
Stir soy milk and vinegar together in a medium sized mixing bowl.
Whisk together the flour, sugar, baking soda and baking powder in a large mixing bowl.
Add the canola oil, water, lemon juice and vanilla extract to soy milk mixture. Mix well with a whisk.
Add soy milk mixture into flour mixture and stir until batter is lump-free.
Pour batter into the prepared baking dish.
Bake in the preheated oven until a knife inserted in the center of the cake comes out clean, about 35 minutes.
Remove from oven and turn onto a baking rack to let cool.
Once cooled, cut in half and then again lenthwise. Liberally spread jam to all pieces. Place the top halves back onto the bottom halves and press down gently.
Wrap in tin foil and freeze for at least 2 hours, If freezing for longer, place tin foiled wrapped cake in a plastic freezer bag.
To make the fruit salad: Wash all fruit and remove stems and cores.
Cut each into uniform bite sized pieces. Place together in a large mixing bowl.
Sprinkle with sugar and gently toss to mix. Cover bowl and refrigerate until using.
To make the Custard: Measure the soy milk into a medium sized saucepan.
Remove ten tablespoons of the milk to a bowl.
Add the sugar and vanilla extract to the saucepan.
Heat and stir over medium heat until sugar has dissolved.
Bring the milk almost to the boil then remove from the heat.
Add the cornstarch to the set aside cold milk, stirring briskly to make a smooth paste.
Add half of the hot milk into the paste, stirring as you do this.
Pour the entire mixture back into the saucepan.
Return the mixture back to the heat and stir until the custard thickens.
Continue stirring as the custard bubbles and thickens. It should stick to the spoon and be of a thick yet pourable consistency.
Remove form heat and let cool for at least an hour.
To make trifle: Remove cake from freezer and cut into uniform cubes.
Place cake in the bottom of a large trifle dish. Be sure to cover the bottom of the dish evenly.
Spoon the fruit salad into the dish, evenly spreading it over the cake with a large spoon. Pour the cooled custard over the fruit, spreading out with a large spoon or spatula to smooth. Spread custard with whipped topping and smooth out with a spatula.
Sprinkle top with toasted sliced almonds. Add raspberries and fresh mint leaves to serve.