Melt 1.5 tablespoons of unsalted butter in a skillet over medium heat. Add the pecan halves and toast them for 4-5 minutes while stirring frequently, until lightly browned and fragrant.

Line an 8x8-inch baking pan with parchment paper and grease it lightly. Set aside.

In a medium saucepan, melt 3 tablespoons of unsalted butter over medium heat until golden brown, about 5 minutes.

In a heatproof bowl over simmering water, combine sweetened condensed milk, chopped white chocolate, and browned butter. Stir continuously for 5-7 minutes until melted and smooth.

Remove from heat, mix in 1 teaspoon of vanilla extract, a pinch of salt, and ½ teaspoon of ground cinnamon. Gently fold in toasted pecans.

Pour the fudge mixture into the prepared pan, smoothing the top. Refrigerate for at least 2 hours to firm up.

Loosen the fudge from the edges of the pan and cut into squares. Store in an airtight container in the refrigerator.