For the Mango Puree: Combine all the ingredients in pot, stir to combine and continuously through cooking until the puree bubbles, about 12 minutes.
For the Candied Cashews: Place the rack in the middle of the oven and preheat to 350 degrees F. Next, line a rimmed cookie sheet with parchment paper. You can also use a jellyroll pan.
In a medium heavy bottom saucepan melt the butter over high heat being careful not to brown the butter. To the melted butter, add the sugar, light corn syrup, and salt and stir to combine. Add the cashews and cook for 3 minutes stirring constantly.
Pour the sugar coated cashews onto the lined baking sheet. With a heat resistant spatula spread the nuts in an even layer. Bake for 12 to 15 minutes until golden brown. Use the heat resistant spatula to stir the nuts half way through the baking to help the nuts develop an beautiful even golden color.
Remove pan from the oven and allow nuts to cool completely. Once cool, break into small clusters.
For the Pastry Cream: Because the pastry cream needs to be removed from the saucepan immediately, prepare ahead and place a bowl, a fine mesh strainer or a food mill, and a heat resistant rubber spatula near the stove.
In a second bowl, whisk together the flour with 1 cup of the sugar. Next, whisk in the eggs until smooth. The mixture will be very thick.
Combine the milk, the remaining cup of sugar, the vanilla bean, and the salt in a medium saucepan. Over medium heat cook the milk mixture being sure to occasionally stir to prevent scorching and a skin from forming. Remove the pan from the heat when it just begins to simmer. While whisking constantly, slowly pour, in a thing stream, about half of the milk into the sugar, flour, egg mixture. Using the same method of pouring slowly and whisking, return the mixture in the bowl to the saucepan with the remaining milk. Return the pan to the stove and cook over medium to medium-low heat while whisking constantly but not vigorously to avoid incorporating air into the pastry cream. Cook the mixture until it thickens. Immediately remove the pan from the stove as soon as the first bubble breaks the surface of the pastry cream.
As soon as the pastry cream is removed from the heat pour the hot pastry cream into the strainer or food mill. Use the spatula to scrape the pan and to push the pastry cream through the sieve, if using.
Place plastic wrap directly on the surface of the cream to prevent a skin from forming. Refrigerate at least several hours, or overnight.
Slice the cake in half horizontaly, brush with simple syrup or a good quality liqueur.
Spread your favorite jam between the layers of cake and cut in squares. Make a mixture of half pastry cream and half whipped cream.
For assembly, place layers of cake on the bottom of a trifle dish. Layer with mango puree, grilled pineapple, candied cashews and the pastry cream/whipped cream mixture continuing layers until the bowl is full. Garnish with coconut and more candied cashews.