In a medium saucepan, combine ginger beer, sugar, cinnamon, and cardamom over medium heat. Add the Bosc pears and poach for about 15 minutes. Soak the pears in syrup for at least 12 hours.

In a large bowl, whisk together the flour, remaining spices, and salt until well blended. Set aside.

In a separate bowl, beat the sugar and eggs together until fluffy. Gradually incorporate the poaching syrup.

Gently fold the dry ingredients into the wet mixture until just combined.

Slice the poached pears into quarters and fold them gently into the batter.

Preheat oven to 350°F (175°C). Pour the batter into a greased loaf pan and bake for 1 hour and 15 minutes, checking doneness with a toothpick.

Remove from oven, cool in the pan for 15 minutes, then transfer to a wire rack to cool completely before serving.