Note: to make oat flour, whiz some oats in a food processor or blender till fine.
The cheeze keeps well in the fridge, so if pressed for time you can double or triple it, and microwave for a few seconds to soften before spreading.
If you don't have a nonstick pan you can lightly butter the bread.
Combine all remaining ingredients, water to salt, in a small pot over medium-high heat. Whisk together as it comes to a boil and immediately turn down to low, stirring continuously for a minute or two, till the cheeze is thickened and creamy. Remove from heat.
Heat a non-stick skillet, or regular if using margarine, on medium.
Spread it on the bread to make sandwiches. This makes quite a bit of cheeze for two sandwiches, so you might want to spread it over three. (But it's so gooey when thick, yum)
Grill on preheated skillet till golden, then flip and do other side. Serve immediately. Great with a salad or veggie sticks and dip.