Preheat oven to 300. Line 9x13 baking pan with parchment paper.
For the BARS: In a large bowl beat butter and sugar at med speed until fluffy and very pale. Beat in vanilla and salt. In a small bowl, combine flour and espresso powder. Add dry ingredients to large bowl in 3rds, scraping and beating until just combined.
Firmly press dough into the baking pan in an even layer using plastic wrap on top with a flat utensil to spread to entire pan. Toss plastic.
Bake about 40 minutes or until very lightly browned and firm but not solid to the touch. Do not over cook. Cool pan on rack about 10 minutes.
Cut bars into 5 strips by 8 strips. (40 bars) Cool completely.
For the GLAZE: In a small saucepan, combine butter, brown sugar, espresso, corn syrup and salt. Boil over moderate heat, swirling the pan, until slightly thickened (1-2 minutes). Remove from heat. When bubbling subsides, pour quickly over shortbread, spreading in an even layer with a spatula. Using a lightly oiled knife, score the glaze without dragging, along cuts. Press an espresso bean in the center of each bar. Cool slightly then separate bars and transfer to a plate.