Add milk to a tall microwave-safe mug or glass. Heat 20-30 seconds until warmed. Add sugar and instant coffee and whisk vigorously until both dissolve and mixture is foamy. Tip: I like to use a handheld milk frother. Make sure you use a very tall container since the milk will splatter.
50 ml soy milk, 60 grams (5 tbsp) granulated sugar, ½ tsp instant coffee
Whisk in oil, walnut butter, and vanilla extract and until well combined.
60 grams (¼ cup) walnut butter, ½ tsp vanilla extract, 26 grams (2 tbsp) oil or melted vegan butter
Add in remaining ingredients and stir with a spoon or spatula. Batter will be thick.
Transfer the batter to your prepared loaf pan. Spread the batter out to fill all the corners. Flatten the top with a silicone/rubber spatula. Preheat oven to 350°F/180°C. Let the brownie batter rest while the oven preheats.Tip: Letting the batter rest before baking gives the oats time to soak up some liquid, resulting in thicker, moister brownies.
Bake 15-20 minutes until a toothpick inserted in the center comes out with a few moist crumbs. Place pan on a wire rack to cool completely.
While you can serve the brownies once cooled, the flavor and sweetness intensify after resting overnight, or at least a few hours. I like to bake them in the morning and have them for dessert in the evening. Chill in the fridge for extra fudgy brownies.