Preheat oven to 350°F. Grease 9x5-in (23x13-cm) 2-L loaf pan; line with parchment paper, leaving some overhang on the long sides.
In bowl, whisk together flour, ground ginger, cinnamon, baking powder, salt, baking soda, cardamom and allspice.
In another bowl, using an electric mixer, beat butter with brown sugar on medium until light and fluffy, 2 to 3 minutes. Beat in eggs, one at a time, scraping bowl after each addition. Beat in molasses.
Stir in flour mixture and buttermilk in 3 additions, beginning and ending with flour mixture, until almost combined. Fold in chocolate and crystalized ginger; scrape into prepared pan.
Pat dry pears; slice enough off bottoms so they stand upright. Carefully nestle into batter.
Bake until puffed and a cake tester inserted into centre comes out clean, covering with foil if browning quickly, 55 to 65 minutes. Let cool in pan on rack for 15 minutes. Turn out onto rack; let cool completely. Serve with Eggnog Creme Anglaise or vanilla ice cream.