Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper. Halve the jalapeños lengthwise and remove the seeds and membranes with a small spoon, leaving the shells intact.
Place a small slice or cube of vegan brie into each jalapeño half. Top with a small spoonful of blueberry preserves and a few thyme leaves if using.
In a small bowl combine the breadcrumbs, olive oil, and a pinch of salt. Sprinkle a small amount over each filled jalapeño half for a slightly crisp finish.
Arrange the filled jalapeños on the prepared baking sheet and bake for 12–15 minutes until the cheese is melted and bubbling and the jalapeños have softened slightly.
Let cool for 2–3 minutes before serving, as the filling will be very hot directly from the oven.
