1. Cut the fruitcake into 1-inch-thick slices and spread them with the raspberry jam. Place 2 or 3 of the cake slices, jam side up, in the bottom of a glass serving bowl 8 or 9 inches across and 3 inches deep.
2. Cut the remaining slices of cake into 1-inch cubes, scatter them over the slices, and sprinkle ½ cup of the almonds on top. Then pour in the sherry and brandy and let the mixture steep at room temperature for at least 30 minutes.
3. In a large chilled bowl, whip the cream with a whisk or a rotary or electric beater until it thickens slightly. Add the sugar and continue to beat until the cream is stiff enough to form unwavering peaks on the beater when it is lifted out of the bowl.
4. To assemble the trifle, set 10 of the best berries aside and scatter the rest over the cake. With a spatula spread the custard across the top. Then gently smooth half of the whipped cream over the surface of the custard.
5. Using a pastry bag fitted with a large rose tip, pipe the remaining whipped cream decoratively around the edge. Garnish the cream with the 10 reserved berries and the remaining ½ cup of almonds.
6. The trifle will be at its best served at once, but it may be refrigerated for an hour or two.
