With the rack in the middle position, preheat the oven to 200°C (400°F).
In a saucepan, bring the maple and corn syrups to a boil. Simmer until a candy thermometer reads 108°C (226°F), about 10 minutes. Remove from the heat, add the cream and stir to combine. Pour the mixture into a 20-cm (8-inch) Pyrex baking dish. Set aside.
In a bowl, combine the flour, baking powder and salt. Set aside.
In another bowl, cream the butter and sugar using an electric mixer. Add the egg and beat until smooth. With the mixer on low, add the dry ingredients, alternating with the milk and vanilla. Using an ice cream scoop, drop about 9 balls of dough, about 45 ml (3 tablespoons) each, into the syrup mixture. Bake until a toothpick inserted in the centre of a ball comes out clean, about 40 minutes.