Preheat oven at 400F
Poke holes all over the Pie Shell crust and bake for around 10 minutes until slightly golden - Remove from oven to cool down
Reduce oven temperature to 375F
Mix the softened butter with the sugar, add the eggs one by one, mix well, add the rum or vanilla extract. it's fine if the batter looks liquidy or a bit lumpy at this point, as long as all the ingredients are blended.
Arrange the pear halves on the baked pie shell. Pour the batter over the pears.
Put the filled pie on a baking tray in the oven. Bake for around 40 to 45 minutes until the batter has puffed up and is golden.
Remove from the oven and cool for half hour. Can be served warm, cold or at room temperature