Make the blondies: Set rack in center of oven and preheat to 350°F.
Butter and flour a 9 x 13" baking pan.
In a small bowl, whisk together the flour, baking powder and salt.
Beat the butter and brown sugar until light and fluffy, about 3 minutes.
Add the eggs, 1 at a time, beating well after each addition.
Beat in the vanilla.
At low speed, mix in the dry ingredients in 3 additions until just blended.
Spread the batter evenly in the prepared pan and bake for 35-40 minutes, or until golden and a cake tester comes out clean.
Make the caramel frosting: Spread the pecans on a baking sheet and toast in the oven for about 8 minutes, or until fragrant and brown (it is good to do this when you remove your blondies from the oven, as the oven will already be hot).
Cool, then chop coarsely.
In a saucepan, combine the cream, brown sugar, sugar, egg yolks, butter and salt.
Cook over medium heat, stirring constantly, until the sugar dissolves and the mixture thickens, about 12 minutes; do not boil.
Strain the mixture into a large bowl, pressing it through a sieve.
Stir in the vanilla, coconut and pecans and cool completely.
Spread the frosting evenly over the blondies.
Cover the pan and refrigerate for 30 minutes.
Cut into 48 small bars and serve cold or at room temperature.
These should be refrigerated if not eaten immediately.