Line an 8x8 inch baking dish with parchment paper.

Add the chocolate chips, sweetened condensed milk, butter, and salt to a medium saucepan and heat over low heat, stirring often, until fully melted and smooth.

Stir in the maple extract.

Pour into the prepared pan and top with chopped walnuts.

Refrigerate for 3 hours, until firm.

Cut into 5 rows by 5 rows for 25 pieces, unless you want bigger pieces.