Line an 8x8-inch baking pan with parchment paper or aluminum foil and lightly grease it with butter.

In a large pot, combine 3 cups of semi-sweet chocolate chips, 1 can of sweetened condensed milk, ¼ cup of unsalted butter, and 1 teaspoon of vanilla extract. Cook on low heat, stirring frequently for about 5 minutes until fully melted and smooth.

Remove the pot from heat and stir in ½ cup of chopped pecans, mixing well to distribute the nuts.

Pour the fudge mixture into the prepared baking pan and use a spatula to smooth the top.

Allow the fudge to cool at room temperature for 3 to 4 hours, or refrigerate for 1 to 2 hours until firm.