Preheat the oven to 350°F with a rack in the center. Grease a standard muffin pan generously with butter (do not skimp!). Place the muffin pan on a parchment-lined baking sheet. , To make the topping: In a small saucepan, combine the butter, maple syrup, brown sugar, and salt over medium heat. Cook, stirring, until butter is melted. Continue cooking until the mixture comes to a full boil (i.e., big bubbles) around the edges of the pan, then set a 30-second timer. By the time it goes off, the mixture may not have boiled in the center of the pot – that’s OK (it’s better to under- than overcook this mixture). Remove the pan from the heat and stir in the pecans and vanilla.
