For me, the most interesting part of baking in humidity was how little liquid you needed to add to the pastry. It's almost as though the pastry mix was absorbing moisture from the air?
Secondly, we had to find a way to keep the butter "solid" enough to mix it into the flour. Not only is Singapore humid, it's also hot. We found the best technique was to put ice cubes in a mixing bowl, then work your butter and flour in a larger mixing bowl nesting on top. This way the butter stayed cool enough for you to work with it.
Finally, the pastry itself seemed to take 3-4 minutes longer to bake. I would suggest you check it after 20 minutes and if it's not baked leave it in for a few minutes more.
So, our final technique is as follows:
Measure out all your ingredients before you start working. I think being able to work quickly helped us create a good pastry.
Put ice cubes into a mixing bowl, then put a larger mixing bowl on top of the one containing ice. Put the butter, flour and ground almonds into this large mixing bowl. With your hands rub the butter into the flour until it resembles breadcrumbs. Next add the icing sugar and continue to rub the mix together.
Add the egg, then quickly mix it all together with your hands. Now add the water one tablespoon at a time. We found 2tbsp was enough. If your pastry does not come together after 2tbsp try adding a touch more. Once combined you should be able to shape the dough into a ball. Wrap this ball of dough in cling film and leave in the fridge overnight.
You can then use this pastry to bake any of my tart recipes: