Prep the oven and pans. Position a rack in the center of the oven and preheat the oven to 400°F. Line a muffin pan with paper liners.
Make the dry mix. In a medium bowl, whisk together the flour, pecan flour, baking powder, and salt.
Make the wet mix. In a large bowl, mix together the maple syrup, melted butter, eggs, and milk.
Make the muffin batter. Gradually mix in the dry ingredients into the wet ingredients until just combined. Mix in the pecans.
Assemble the muffins. Use a 1-Tablespoon cookie dough scoop to fill each paper liner with 4 generous Tablespoons of the batter. Bake the muffins. Bake for 22 to 24 minutes, or until the muffins are domed and a skewer inserted into the center of a muffin comes out with a few crumbs attached. Cool in the muffin pan on a wire rack for 10 minutes, then turn the muffins out onto the rack to cool completely. Once the muffins are cool, make the glaze. Make the glaze. In a medium bowl, mix together the confectioners’ sugar, maple syrup, melted butter, and water until a thick glaze forms.
Glaze the muffins. Working quickly, hold a muffin upside down, dip its top into the glaze, and quickly turn it right side up on a wire rack. Garnish with a pecan half. Repeat with remaining muffins.
Serve and store. Serve at room temperature. The muffins can stored at room temperature, under a cake dome or in an airtight container, for up to 2 days.