Peel and core the pear and cut into cubes of about 7 cm. The pear should become soft, but not lose its shape. Transfer to a plate, cool.
Pour the cream into a saucepan, add the chopped cinnamon stick and bring to a boil. Remove from stove and let steep 10 minutes. Strain and heat the cream again.
Finely chop or chop the chocolate, pour over hot cream and stir with a whisk until a homogeneous glossy mass. Cool to room temperature.
Beat egg whites until stiff, adding sugar in two batches. Stir 1/3 of the egg whites into the chocolate, then the remaining egg whites and the pear cubes. Divide the mousse among 4 bowls or glasses and refrigerate for 2 hours.
Before serving, peel the pear and cut into 8 pieces. Melt the butter in a frying pan, put the pear slices and sprinkle with sugar. Caramelize the pear for 2-3 minutes. Cool slightly and put on mousse. Drizzle with chocolate icing and garnish with a broken cinnamon stick.