Preheat the oven to 350 degrees F and grease (or use liners) 2 12 cup muffin tins.
In a large bowl, whisk together the flour, baking powder, salt and 1 tablespoon espresso powder. In a separate bowl or large measuring cup, combine the coffee, buttermilk, and vanilla. Set aside.
Using a mixer, beat together 1 1/2 cups softened butter with 2 cups sugar until light and fluffy, 3 to 5 minutes. Beat in the eggs, one at a time, waiting until each egg is fully incorporated before adding another.
Gently beat the flour and coffee mixtures into the butter mixture, alternating between wet and dry, one third of each at a time. Scrape down to bowl as needed to ensure all of the ingredients are mixed.
Divide the batter between the muffin cups, filling each one 2/3 to 3/4 full. Bake until the muffins have risen and a toothpick inserted comes out clean, 20 to 30 minutes. Rotate the pans halfway through for even baking. Remove the muffins and cool completely.
Meanwhile, in a medium bowl, combine the remaining 1 1/2 cups sugar and 1 to 2 tablespoons espresso powder. Brush the cooled muffins on all sides with melted butter, then roll in the sugar mixture. Serve immediately.