Blueberry Crisp Tart

Name: Blueberry Crisp Tart
Ingredients: For the crust:; 8 tablespoons (1 stick) unsalted butter, melted; 1/4 cup sugar; 1/8 teaspoon salt; 3/4 teaspoon vanilla extract; 1 cup all-purpose flour; For the filling:; 2 1/2 cups (11/4 pints) fresh blueberries, picked over and washed; Juice of 1 lemon; 1 tablespoon sugar; For the crisp topping:; 1/4 cup all-purpose flour; 1/4 cup rolled oats; Pinch of ground cinnamon; Pinch of salt; 2 tablespoons unsalted butter, at room temperature; Vanilla ice cream, for serving (optional)