Preheat oven to 350 degrees F.
Combine butter, egg, milk, maple syrup and vanilla. Add chopped nuts and gently pour into tart shell. Garnish with extra nuts if you like.
Bake for 25 to 30 minutes until top of tart is puffed and bubbly and crust is starting to brown. Cool for 20 minutes before removing from tart pan.
Can be served warm or at room temperature. Add a dollop of whipped cream for an extra special treat