Drain the pineapple. Cut the pineapple into small pieces, except for one slice. Puree 3/4 of the pineapple pieces. Stir in lemon juice, rum and vanilla sugar
Separate eggs. Beat the egg whites until stiff, adding sugar. Stir in egg yolk. Mix mascarpone, pineapple puree and coconut flakes. Carefully fold in first the beaten egg white mixture, then the remaining pineapple pieces
Cut out 6 strips (each approx. 10 x 32 cm) from parchment paper. Place one strip each around a soufflé dish (approx. 9 cm Ø; 1/8 l capacity) so that the parchment paper protrudes 2-3 cm over the edge
Pour in parfait mass. Leave in the freezer for 4-5 hours (preferably overnight). Remove paper. Cut the rest of the pineapple into pieces. Decorate parfaits with pineapple and coconut