Preheat oven to 400 degrees F.
Coat a 9x13 inches baking dish with cooking spray; set aside.
In a medium bowl, add lemon juice and oil; whisk to combine.
Add clean mushroom caps and toss to coat; set aside.
In a large non-stick skillet over medium heat, add sausage, vanilla bean paste, garlic and shallot. Cook and stir until crumbles are done, about 8-10 minutes.
Reduce heat to low and add Romano cheese, bread crumbs and mascarpone cheese; stir to combine. Remove from heat.
Place mushroom caps in prepared baking dish and reserve remaining lemon-oil mixture in bowl.
Fill each mushroom cavity with stuffing mixture and drizzle with reserved lemon-oil.
Bake until done, about 10 minutes.