Drain the pears on a sieve. Coarsely chop 50 g of chocolate and melt in a pot at low heat. Stir 3-4 tablespoons of milk and starch until smooth. Stir the remaining milk into the melted chocolate.
Add cocoa, salt, sugar and vanilla sugar and heat while stirring. Stir in cornflour and let the sauce boil for 1/2 minute. Whip the cream until stiff and fill into a piping bag with star-shaped spout.
Spread ice cream scoops and pear halves in 4 glass bowls. Pour warm chocolate sauce over them. Garnish with cream tuffs. Grate the rest of the chocolate with a peeler over the cream. Serve immediately.