Cut butter into cubes. Knead flour, sugar, butter, baking powder and egg to a smooth short pastry. Press the dough with floured hands into a springform pan (26 cm Ø) in such a way that an approx. 3 cm high rim is created.
Prick the bottom of the pastry several times with a fork and put the mould in a cool place. Drain the mandarins on a sieve and collect the juice. Bring 3/8 litres of milk and sugar to the boil. Mix the pudding powder with the remaining milk until smooth.
Add to the boiling milk and bring to the boil while stirring. Stir in sour cream and put it immediately into the springform pan. Smooth it down and spread the mandarins on top. Bake in the preheated oven (electric: 175°C/ gas: level 2) for 70-75 minutes.
Leave to cool in the mould (preferably overnight). Measure out 1/4 litre of tangerine juice and mix it gradually with the cake glaze powder in a pot. Bring to the boil briefly while stirring. Allow to cool for a few minutes, then pour evenly over the mandarins.
Let the casting cool down and solidify. Serve sprinkled with flaked almonds. Makes about 16 pieces.