Boil crème anglaise, milk, cream, and vanilla seeds in a saucepan.
Whisk egg yolks and sugar until fluffy, then combine with the hot cream mixture.
Stir the custard over medium heat until thickened, then strain and stir in ground ginger.
Chill the custard thoroughly, then churn in an ice-cream machine and freeze.
Whisk crème fraîche, cream, and ginger syrup together and chill for 30 minutes.
Preheat oven to 170°C and grease a tin with butter.
Mix the dry cake ingredients in a large bowl.
Combine the melted butter, syrup, and demerara sugar in a second bowl.
Whisk the egg and milk together in a third bowl.
Combine all cake components, pour into the tin, and bake for 8 to 10 minutes.
Dust 100g of cake cubes with icing sugar and bake at 170°C for 3 minutes to toast.
Combine the diced pear, confit ginger, and toasted cake cubes.
Layer the crumble, ice cream, and crème mixture in bowls, drizzling with stout and ginger ale.