Line an 8x8 inch square pan with parchment paper, leaving it hang over on the sides.
In a medium saucepan over low heat, melt the chocolate chips, sweetened condensed milk, and butter, stirring until smooth.
Remove from heat and stir in vanilla extract. Spread evenly in lined pan.
Top with crushed pretzels and sea salt. Gently press down on topping to ensure it sticks to top of fudge. Chill for three hours or until firm. Remove from pan and cut into squares.