Pie crust:
Combine flour, butter, and icing sugar in a food processor and mix until it resembles coarse crumbs.
Add egg yolks one at a time, then gradually add cold water until the mixture forms a ball.
Remove the dough from the processor and knead for 30 seconds on a lightly floured surface.
Wrap it in plastic wrap and refrigerate for at least 1 hour.
Remove the dough from the refrigerator and roll it out into a 12-inch (30 cm) circle, about 1/3 inch (0.7 cm) thick.
Place it in a 9-inch (23 cm) metal or glass pie dish, greased.
Refrigerate while preparing the filling.
Preheat the oven to 400 F (200 C).
Filling:
Combine flour, brown sugar, and butter in a food processor and mix until it resembles coarse crumbs. Set aside.
In a bowl, whisk together baking powder and boiling water.
Add corn syrup, Golden Syrup, and molasses. Mix well.
Remove the pie crust from the refrigerator and pour in the molasses mixture.
Sprinkle the flour, butter, and brown sugar mixture on top.
Bake on the lower rack for 10 minutes.
Reduce oven temperature to 350 F (180 C) and move the pie to the middle rack. Continue baking for 30-35 minutes, or until the filling is set but still slightly jiggly.
Remove from the oven and let cool to room temperature before serving with vanilla ice cream.