This version stays crunchy in milk for a long time, but produces a cereal that is too crunchy for toddlers to eat plain.
1 cup oat flour
1/2 cup non-GMO cornstarch or arrowroot starch
1/4 cup whole cane sugar
1 teaspoon sea salt
1 teaspoon baking powder
4 tablespoons all-purpose flour OR vital wheat gluten (the flour creates a more elastic dough, surprisingly)
10 tablespoons (5/8 cup) boiling water
Preheat the oven to 350F.
Whisk the dry ingredients together in a large bowl and set aside.
Pour the boiling water over and stir until the dough comes together in a coherent ball. The dough should be very soft and just slightly sticky.
Set out a piece of parchment paper and place the ball of dough on it. Press into a disc about 1-inch thick, then place another piece of parchment over the top of the dough and roll until the dough is about 1/4-inch thick, about the thickness of two nickels.
Using a pizza cutter or a very sharp knife, cut the dough into small squares about 1/2″ x 1/2″.
Lift the entire piece of parchment paper onto a baking sheet and bake until the surface is dry, the dough is puffed, and it’s just beginning to brown, 8-9 minutes.
Remove from the oven, reduce heat to 300F, then break the dough into the predefined pieces. Return to the oven for 15-20 minutes, stirring every five minutes, until the pieces are crisp and very dry.