For the rhubarb compotée:

Trim the rhubarb, cut into cubes.
Cook the rhubarb, water and sugar over a moderate heat for around 30 minutes, stirring regularly until a compote is obtained. Allow to cool, then refrigerate.

For the strawberry mousse:

Wash, hull and slice the strawberries. Sprinkle half the strawberries with icing sugar and blend.
Heat the milk and agar agar and boil for 2 minutes, stirring, then add the crème fraîche.
Pour the mixture onto the blended strawberries. Blend for another 30 seconds. Pour into a bowl and add the reserved strawberry pieces.
Divide the mousse between small verrines and refrigerate for 2 hours.

Feuillantines:

Preheat the oven to 180°C (th.6)
Place the slightly salted butter in a pan with the pineapple juice and heat until just melted.
Cut the filo pastry sheet into pieces of the desired shape with a knife. Brush with melted butter, sprinkle with brown sugar and crumbled Gavottes.  Place in the oven to bake for approx 10 minutes at 180°C until lightly browned.
Remove the mousse from the refrigerator, cover with the compote and serve with the feuillantines. Enjoy!