Heat oven to 375 F

fit pie crust into a 9 inch pie dish and crimp edges

dock the bottom with a fork and line with parchment then fill with pie weights

bake until edges are lightly golden about 15 minutes then remove weights and bake 5 minutes more

cool completely and brush with egg wash during the last 2 minutes optional.

In a saucepan whisk sugar cornstarch cocoa and salt

slowly whisk in milk until smooth then cook over medium heat whisking constantly until thickened and bubbling 6 to 8 minutes

whisk egg yolks in a bowl then temper with a ladle of hot mixture and whisk back into the saucepan

cook 1 to 2 minutes until glossy and thick

remove from heat and stir in chopped chocolate butter and vanilla until smooth.

Strain filling through a fine mesh sieve into the cooled crust and press plastic wrap directly onto the surface

chill until set at least 4 hours

whip cream with powdered sugar and vanilla to medium peaks and spread or pipe over the pie

garnish with chocolate shavings and slice cold.