Preheat oven to 350°F with rack in middle.

Stir together all the crust ingredients and press evenly onto bottom and 3/4 inch up side of tart pan. Bake until firm, about 10 minutes. Cool on a rack 15 to 20 minute.

Bring cream for the filling to a boil, then pour chocolate and the maple syrup for the filling into the pan, let stand 5 minutes. Gently stir until smooth. Let the chocolate mixture cool until it is almost room temperature.

Whisk together eggs, vanilla, and salt in another bowl, then stir into melted chocolate.

Pour filling into cooled crust. Bake about 20 minutes until filling is set about 3 inches from edge but center is still wobbly. The center will continue to set as the tart cools. 

Cool completely in pan on rack, about 1 hour.

Next make the glaze. Bring cream to a boil and remove from heat. Stir in the 1 ¾ oz of chocolate until smooth. Stir in maple syrup, then warm water

Pour glaze onto cooled tart, then tilt and rotate tart so glaze coats top evenly. Let stand until glaze is set, about 1 hour.