First up, mix the ground flaxseed and hot water together to make flax eggs. Add 3 Tablespoons ground flaxseeds to a bowl and then pour ½ cup (120ml) of hot water from the kettle over the top. Leave it to sit and thicken while you prepare the other ingredients.
Preheat the oven to 350°F (180°C) and spray a 9x9 square baking dish with non-stick spray and line it with parchment paper so that there is overhang on either side.
Sift all purpose flour and cocoa powder into a mixing bowl and add baking powder and salt. Mix together.
Add vegan butter and ½ cup of vegan chocolate chips to a microwave safe bowl and microwave in 30-second intervals, bringing it out to stir every 30-seconds until melted.
Add peanut butter, flax eggs, white granulated sugar and vanilla extract to the melted butter and chocolate mix and whisk it in with a hand whisk.
Add wet ingredients to dry and mix it into a thick batter.
Add a cup of vegan chocolate chips and mix them in.
Transfer to your prepared 9x9 square baking dish and smooth down.
Dollop peanut butter onto the top of the brownies with a teaspoon. Use a butter knife to swirl the peanut butter into the top of the brownies.
Bake for 40 minutes. The brownies should look dry and set on top.
Let them cool and firm up in the pan for 15 minutes before you lift them out using the parchment paper overhang. If you try to lift them out using the parchment paper overhang and they seem like they may break, then leave them to cool for a bit longer before lifting them out.
Place them onto a wooden board and then place them into the fridge for around 2 hours until completely cold. When the brownies are completely cold, cut into squares and serve.