Strawberry coulis: Combine ingredients in a small pot, bring to a boil, and simmer for 12 minutes. Puree until smooth.
Mango coulis: Combine ingredients in a food processor and process until smooth.
In a small (2-quart) trifle dish or pretty glass bowl layer 1 1/2 cups of cake pieces. Top with 1 cup of mango pieces and 1 cup of mango coulis. Layer 1 1/2 cups of cake pieces and top with 1 cup of strawberries and 1 cup of strawberry coulis. Layer 1 1/2 cups of cake pieces and top with remaining mangos and mango coulis. Layer remaining cake pieces and top with remaining strawberries and strawberry coulis. Spread whipped cream over entire surface and chill until ready to serve. Garnish with mint.