Begin by preheating the oven to 350 degrees F. Line your muffin tin(s) with paper liners. You'll need 16 or so. Set aside.
In a large bowl, add the flour, baking powder, and salt. Whisk to combine.
Then, beat in the maple syrup and heavy cream at medium speed. Add the eggs, one a time, beating after each addition. Beat in the butter and vanilla extract until just smooth. Then, fold in the chopped walnuts.
Fill the prepared muffin liners about 3/4 full of batter. Bake for 22-24 minutes or until a toothpick inserted near the center of a cupcake comes out clean.
Allow the cupcakes to cool in the pan for about 5 minutes before removing and transferring them to a wire rack to finish cooling.
In the meantime, prepare the Maple Frosting. In a medium bowl, beat together the butter, sugar, salt, and maple syrup until fluffy. If the frosting is too thick, add a splash of heavy cream.
Add the filling to a piping bag fitted with a large close-star tip. Pipe the frosting onto the cooled cupcakes. Top each cupcake with a walnut half.