Preheat your oven to 375°F (190°C).
Gently clean the portobello caps with a damp cloth and remove the stems. Carefully scrape out any gills using a spoon.
In a large mixing bowl, combine lump crab meat, panko breadcrumbs, sliced green onions, boursin cheese, egg, dijon mustard, worcestershire sauce, and tabasco sauce. Stir gently until all ingredients are well incorporated.
Spoon generous amounts of the crab mixture into each portobello cap, pressing down lightly.
Place the stuffed mushrooms on a baking sheet lined with parchment paper and bake for about 15 minutes or until golden brown on top.
Once baked, remove from the oven and let them cool slightly before serving.