In a large bowl, combine the flour, baking powder, cinnamon, and sea salt and stir well until combined (dry ingredients).
In a separate mixing bowl, whisk together the oat milk, oil, vanilla extract and the egg yolks, (separating the egg whites into a separate large bowl or a stand mixer) until well combined (wet ingredients).
Use a stand mixer or electric hand mixer to fluff the egg whites until they are very frothy and form stiff peaks.
Pour the wet ingredients into the bowl with the dry ingredients and stir well until all the clumps of flour are out.
Fold in the egg whites until incorporated into the waffle batter.
Plug in your Belgian waffle iron and make waffles according to the manufacturer instructions for your maker. Pour the waffle batter onto the hot waffle iron, place the cover, and cook until golden brown. My BELLA waffle maker takes about ¾ to 1 cup of batter per waffle and I set it on the highest heat setting.
Repeat for the remaining waffle batter (my waffle maker makes 4 large Belgian waffles out of the batter). If you'd like, you can store finished waffles on a baking sheet while the rest of the waffles are cooking.
Serve waffles immediately with butter, pure maple syrup, whipped cream, and strawberries.