Soak red lentils for 1-2 hours in water. If you would like to have them for breakfast, then soak them overnight no problem. If you worry about lectins (see above for more explanation) then you can also cook them first in plain water.
When you are ready to make your vegan waffle batter, discard the water and blend the soaked red lentils with non-dairy milk and the optional vanilla extract until smooth.
To finish the batter, pour the blended mixture in the bowl, add the flax egg and mix them with a whisk.
Now you are ready to heat up your waffle maker and have a crispy and delicious not to mention vegan and gluten-free breakfast. (See notes on how to cook the waffles crispy)
I am pretty sure that all waffle makers are different, but to get extra crispy waffles with mine I follow these steps:
Turn waffle maker on and wait for it to heat up completely.
Even if they said that it is a non-stick one, I coat it with oil spray generously.
Pour the waffle batter, but just enough so that it doesn't overflow. Mine works with less then 1/2 cup.
Close the lid and wait for 2-3 minutes, then turn the waffle maker off but leave the lid closed for another 2-3 minutes. This way it is not over-cooked (dark brown) but cooks all the way through while getting a drier, crispier crust.