Preheat your oven to 350°F. Grease a 13x9-inch pan with butter.

Make the crust: In a large bowl, cream the butter and sugar. Add the flour and stir until just combined. The dough will be crumbly. Press the mixture firmly and evenly into the pan. Bake for 20 minutes, or until it's just beginning to turn golden.

While the crust is baking, make the filling. In a large bowl, beat the brown sugar and eggs until well combined.

In a small bowl, whisk together the flour, baking powder, and salt. Add the flour mixture and beat until just combined. Stir in the vanilla, shredded coconut, and pecans.

Pour the pecan-coconut filling over the top of the warm crust and bake for 20 minutes more. Let the bars cool in the pan on top of a wire rack.

Make the frosting. In the bowl of a stand mixer using the whisk attachment, cream the butter for a few seconds, just until smooth. Add the sugar and the vanilla and beat for about 2 minutes on medium-high speed, until fluffy and light.

Spread the frosting evenly over the top of the cooled bars. I suggest you tent the bars with aluminum foil and refrigerate them for about 20 minutes before cutting, so that the frosting will firm up a bit and be easier to neatly slice. Cut into 24 small squares and garnish each one with either a sprinkling of chopped pecans or set 1 pecan in the middle of the top of each bar.