Combine all of the dry ingredients in the bowl of an electric mixer using the paddle attachment.
Slowly pour in the water, then the butter, while the mixer is on.
Refrigerate the batter, because once it firms up it is easier to spread.
Preheat a convection oven to 160°C / 325°F.
Spread a paper-thin layer of batter on a nonstick rubber mat.
Bake until the tuile is golden brown, about 6 minutes.
Remove it from the oven and slide the nonstick rubber mat onto a marble surface or stainless steel table. Wait a few seconds for it cool down. Use a 3.75-cm / 1.5-in square cutter to cut squares out.
If the tuile becomes too hard and it cracks when it is being cut, return it to the oven to soften. This procedure may need to be repeated a few times before the amount of tuiles that is needed is obtained.
Reserve in an airtight container at room temperature. Refresh daily in a hot oven for 2 minutes; discard after 3 days.