Spray a 9 1/2-inch tart pan with a removable bottom with cooking spray and lightly flour the pan, shaking to remove excess.
Melt the butter and chocolate chips in a glass or metal bowl over a pan filled with 1 inch or so of simmering water. Stir until the butter and chocolate chips have melted and the mixture is smooth. Set aside to cool.
Beat the eggs, sugar, instant espresso and the vanilla extract in a stand mixer until blended. Add the cooled chocolate mixture and blend to combine. In a smaller bowl, stir together the flour, baking powder and kosher salt and then add to the bowl of the stand mixer and mix just until combined. Stir in half of the chopped pecans and pour into the prepared pan. Top with the rest of the chopped pecans.
Bake for 34-45 minutes or until the top begins to crack and the middle is somewhat set but still soft. The pie will deflate somewhat as it cools.
Top the brownie pie with the frosting. Remove from the tin and serve cake at room temperature.
For the frosting
Add the yolks to a small saucepan and beat with a hand mixer until yolks thicken and begin to ribbon, about 2-3 minutes. Add evaporated milk, sugar and vanilla and mix. Add butter and bring to medium heat, stirring constantly, for about 10 minutes or until mixture becomes golden brown and thickens. Remove from the heat and add the coconut and pecans. Cool to room temperature and frost your pie, cake or cupcakes..