Pour the chocolate chips into your large bowl. Add the sweetened condensed milk on top. Add the butter to the bowl as well.

Put the bowl in the microwave now. Heat the mixture on high for one minute. Take it out and stir it gently.

Heat it for another thirty seconds if needed. Stir until the mixture is very smooth. All the chips should be melted completely.

Stir in the vanilla extract and the walnuts. Mix them until they are spread out evenly. The fudge will look shiny and thick.

Spread the mixture into your prepared pan. Use your spatula to smooth the top. Make it as flat as possible.

Place the pan in the refrigerator. Let it chill for at least two hours. It needs to be firm before cutting.