Melt the butter in a medium saucepan over medium-high heat.
½ cup salted butter
Stir in the brown sugar, granulated sugar, heavy cream, and baking soda.
1 cup light brown sugar, 1 cup granulated sugar, 6 ounces heavy cream, ½ teaspoon baking soda
While continuously stirring, allow the mixture to come to a simmer until it has reached the softball stage at 235°F.
Remove the pot from the heat and stir in the pecans and vanilla extract. Continue to stir until the mixed mixture starts to thicken and lightens in color.