Preheat oven to 350°F (175°C).
Heat the vegan butter in a medium saucepan, or cast-iron cocotte. Once melted, add the onion, garlic, and a pinch of salt. Sautée for about 5 minutes, or until onions are caramelized. Add the maple syrup and sautée for another 1-2 minutes.
Next, add the mushrooms and carrot and sautée for 5-7 minutes. Deglaze the pan with the soy sauce and balsamic vinegar.
Dilute the flour in 2 tbsp of water and add it to the saucepan. Stir to combine. Add the ground black pepper and vegan pesto and cook for another minute, stirring regularly.
Divide the mushroom filling between three small ramekins (I used 0.25-Q ones), filling almost all the way to the top.
Cut 3 rounds of puff pastry a bit larger than the size of your ramekins. Cover each ramekin with the puff pastry rounds and use a fork to slightly press the edges. Using a small knife, make 2-3 holes on the puff pastry, this will prevent the pastry from cracking.
To create the little Hogwarts crest, make sure your puff pastry is very cold, straight from the fridge. This will make it easier to work with. Using a sharp knife, cut a little H letter and a crest in shape of the Hogwarts logo. Slightly press them on top of each ramekins.
In a small bowl, combine the almond milk with the maple syrup. Carefully brush the puff pastry with the maple/almond milk. Bake in the preheated oven for about 30 minutes, or until golden brown.
Let it cool a few minutes before serving!