Citrus cake with white chocolate truffle and meringue like a lemon pie

For the lemon curd:
140 g sugar
12 to 15 g corn starch
200 g whole egg
50 g egg yolks (we reserve the egg whites for the meringue)
1.5 dl juice of half a lime and half a lemon
Zest of one lemon, one tangerine and one lime
160 g butter
For the white chocolate truffle:
400 ml 35% cream “120 ml + 280 ml”
170 g good quality white chocolate
For the meringue:
Leftover egg whites from making the lemon curd, double the amount of sugar plus 50 ml water
For the brioche:
120 ml whole milk
20 g fresh yeast
65 g soft flour or baking flour
390 g soft flour or baking flour
240 gr whole egg
75 gr sugar
8 gr salt
200 gr butter
Zest of one orange peel
1 teaspoon orange blossom water