The combination of dark brown sugar, vanilla, and pecans in these muffins make them taste just like pecan pie.
Preheat oven to 350 degrees. Line a standard 12-cup muffin tin with baking cups. Spread pecans on a baking sheet and bake until fragrant, about 12 minutes. Cool 15 minutes, then coarsely chop. In a medium bowl, whisk together flour, baking powder, and salt. In a separate bowl, whisk together sugar, eggs, butter, milk, and vanilla. Stir wet ingredients into dry ingredients, then stir in pecans.
Divide batter evenly between muffin cups,adding a scant 1/4 cup to each. Top each with a single pecan half or more chopped nuts, and sanding sugar. Bake until tops spring back when lightly touched, about 20 minutes. Cool in pans 5 minutes, then remove to wire rack to cool completely.