Dry roast rolled oats in a pan on low heat for 2 minutes.

Cool for 3-4 minutes and grind in a mixer at high speed into a fine powder.

Preheat oven to 350F (180 degrees Celsius).

Line a brownie pan with parchment paper or grease aluminum foil with cooking spray.

Sieve the powdered oats flour and measure 1/2 cup.

Add baking powder, baking soda, and salt to the oats flour and mix evenly.

Mash the banana in a bowl using a fork.

Add flaxseed meal to 3 tablespoons of lukewarm water.

Stir and mix until frothy.

In a large bowl, beat sugar, oil, and flaxseed mixture using an electric mixer for about 2 minutes.

Add vanilla extract and cocoa powder and beat at low speed until smooth and creamy.

Do not overbeat.

Add mashed bananas and flour to the bowl.

Add chopped walnuts and chocolate chips.

Stir and mix well until the oats flour is incorporated.

Grease the baking pan and dust with flour; tap off excess.

Pour the batter into the prepared pan and bake for 35-40 minutes.

Check for doneness: edges baked through, center set, shiny top with cracking.

Cool brownies completely in the pan on a wire rack for one hour.

Cut into neat squares after cooling.

Store in an airtight container.

Serve with coffee, ice cream, or warm chocolate ganache.