In a small mixing bowl combine the chai seeds and oat milk, stir together and set aside while you prepare the other ingredients.
Preheat the oven to 350 degrees F and line a 9 x13 pan with parchment paper.
In a medium bowl add the flour, cocoa powder, salt, and baking powder. Stir together a couple of times, set aside.
Melt the vegan butter, either on the stove top over medium-low heat or the microwave in 30-second intervals. Measure the butter in a measuring cup making sure you have the full 1/2 cup needed for the recipe.
Using a stand mixer or hand mixer and a large mixing bowl, beat together the melted vegan butter and sugars. Mix in the chia seeds and vanilla extract.
Add the flour mixture to the butter, and sugar mixture and mix together until just combined.
Fold in 1 cup of the chocolate chips. Gently pour the mixture into the pan, using a spoon or your hands to even it out. Scatter the remaining 1/4 cup of chocolate chips over the top.
Bake in the preheated oven for 37-42 minutes. Note the brownies will look done around the edges but look a little underdone, they aren't! As long as you can gently touch the center of the brownies and have it keeps its form, the brownies are done.
Remove from the oven, allow to cool on a cooling rack the pan for 15-30 minutes, then pull the brownies out of the pan, using the parchment paper. Let the brownies continue to rest for another 30-60 minutes before cutting.