Preheat the oven to 350 degrees.
For the dough, mix the oat flour and date paste in a large bowl. The dough should be very thick and not too wet.
Press out 3 tbsp of the dough into 4 rectangular shapes on a nonstick or lined baking sheet. These are the bottoms of the poptarts.
Bake just the bottoms for 10 minutes.
While the bottoms are baking, make the filling/frosting by blending the soaked cashews, stevia, vanilla extract, almond extract, and water until everything is incorporated and it's thick and creamy. You'll have to stop it a few times and use a spatula to scrape down the sides so everything gets mixed in. I use a lot of frosting on top, so if you don't want as much, you could probably cut the frosting ingredients half and have enough for the filling and a thinner layer of frosting than shown in these photos.
When the bottoms have baked for 10 minutes, set the pan on the counter and carefully (the pan is hot!) spoon about 2 tbsp of the filling onto each poptart bottom. DO NOT overfill! There will be a lot of the frosting mixture leftover, which you'll put on top of the finished poptarts.
Divide the remaining dough into four pieces, one for each poptart top – shape it roughly with your hands, and place it on top of the filled bottoms, carefully sealing the edges with your fingers (remember, the pan is hot, so be careful!). A bit of filling may seep out when you're assembling, which is fine. Do the best you can and have fun with it ????
Use a fork to gently press the edges of the poptart to seal them together.
Bake the full poptarts for another 10 minutes. Chill the filling/frosting mixture in the fridge while the poptarts finish baking.
Once they're done, allow the poptarts to cool on the pan for 15 minutes before removing from the pan to cool completely.
When the poptarts are cool, spread the remaining frosting on top, and add sprinkles if desired (I just use these for photos, the birthday cake flavor comes from the filling/frosting!).
Store leftovers in the refrigerator. These are best enjoyed fresh, or 2-3 days after baking.