Mix flour, powdered sugar, and butter together with a hand mixer until you get something that resembles small breadcrumbs. Whisk the egg and lime juice in, then gather the dough on a flour-dusted surface—knead until smooth and pliable. Refrigerate for 30 minutes. Roll out the dough to a thickness of 3-4 mm and cut out 8 circles approximately 8cm. Bake the bases for 8-10 minutes at 200 degrees Celsius (392 degrees Fahrenheit) (conventional oven) until they are nicely golden. Let cool.  

Soak the gelatin in cold water. Bring mango, lemon juice, and sugar to a brief boil and let it simmer for 10 minutes until the mango is tender. Blend with an immersion blender until smooth, then stir the gelatin into the warm mixture. Pour the puree into half-sphere silicone molds of 4cm and freeze for a minimum of 2 hours.  

Soak the gelatin in cold water. Bring lemon juice and sugar to a boil until the sugar has dissolved. Remove from heat and dissolve the gelatin in the warm mixture. Fold in the skyr. Whip the cream to a light foam and fold in the lemon/skyr mixture. Distribute into half-sphere silicone molds of 7cm (fill 2/3 full) and press the now frozen mango fillings into them. Top up with a bit more mousse and smooth out. Freeze. Spray and decorate the frozen cakes, thaw for one hour before serving.