Line a 8x8 pan with tinfoil and spray heavily with a non-stick spray.

In a large, heavy saucepan, combine sweet and condensed milk and liqueur.

Bring to a simmer over medium heat; until it reaches 234°

Remove from heat.

Stir in the chocolate morsels, stirring until melted and smooth. Add the walnuts and vanilla, stirring well to combine.

Spread evenly into the lined pan.

Refrigerate for 2 hours or more.

Lift foil onto cutting board, peel fudge from foil and cut into uniform squares to serve.