Melt vegan butter over medium heat. Add sliced apples, cook 3–4 minutes, then drizzle maple syrup and cook until glossy. Cool slightly.
Place vegan brie in center of puff pastry, spread apple butter on top, then spoon caramelized apples over it. Fold edges to seal.
Brush pastry with plant milk and sprinkle coarse sugar.
Preheat oven to 400°F (200°C). Bake 20–25 minutes until golden brown and crisp.
Let rest 10 minutes before slicing. Garnish with thyme and serve warm.
