Preparation time : half an hour
Preheat the oven to 170 °C. Grease a ring mold (20 cm ø) with melted butter or oil. Dust the bottom and sides evenly with flour and tap off excess flour.
Shape chocolate in a glass bowl and stir over gently simmering water until liquid. Remove from kitchen heat.
In a small wide bowl, beat butter and sugar with a hand mixer until blended. Gradually add the egg yolks and beat thoroughly. Then add the chocolate and stir until well blended.
Pour the mixture into a large wide-mouth mold. Using a metal spoon, alternately fold in the sifted flour, baking powder and milk.
Egg whites into a small, clean, dry Weitling mold and beat until stiff peaks form. Fold into flour mixture with a metal spoon. Stir until well blended and fairly smooth.
Pour half of the mixture into the prepared mold. Cut pears into narrow slices and arrange on top of batter.Spoon remaining batter on top and smooth surface. Bake for about 40 min (a wooden skewer inserted into the center of the cake should come away cleanly from the dough).
Bake the cake in the pan for 6 min, then turn out onto a cooling rack and cool.
For the glaze : Heat the pear juice in a small saucepan and simmer the liquid down to a tablespoon. Remove from heat and stir in powdered sugar and butter. Mix with water