Microwave chocolate chips in a large bowl, stirring occasionally until melted.
Whisk egg yolks, sugar and salt in medium bowl until combined.
Bring half and half to a simmer in small saucepan over medium heat.
Whisking constantly, slowly add hot half and half to egg yolk mixture until incorporated.
Return half and half mixture to saucepan and cook over low heat, whisking constantly until thickened about 1 minute.
Stir half and half mixture into melted chocolate until combined.
Let cook slightly, about 8 minutes.
Meanwhile whip cream on medium low speed with a handheld or stand mixer fitted with whisk attachment until foamy, about 1 minute.
Increase speed to high and whip until thick, 1-3 minutes.
Gently whisk ⅓ of whipped cream into cooled chocolate mixture and fold in the remaining until no white streaks remain.
Cover and refrigerate at least 3 hours, or until ready to assemble pie (filling can be made up to 24 hours in advance.)
Heat oven to 275 degrees farenheit.
Grease a pie plate and dust well with cornstarch, using a pastry brush to distribute evenly.
Combine sugar and 1 tablespoon cornstarch in bowl.
Using a handheld or stand mixer fitted with whisk attachment, whip egg whites and cream of tartar on low speed until foamy, about 1 minute. Increase speed to medium high and whip to soft, billowy mounds, about 1 to 3 minutes.
Gradually add sugar mixture and whip until glossy, stiff peaks, 3 to 5 minutes. Stiff peaks will stand straight up when you hold the whisk upright.
Add vanilla and whip until incorporated.
Spread meringue into prepared pie plate, following all the contours of the pie plate and over the edges.
Bake for 1 ½ hours. Rotate pie plate, reduce temperature to 200 degrees farenheit and bake until completely dried out, about 1 hour longer.
Let cool completely, about 30 minutes.
Spoon chocolate filling into pie shell.
Whisk cold heavy cream and sugar on low speed until foamy, about 1 minute. Increase speed to high and whip until stiff peaks form, 1 to 3 minutes.
Spread whipped cream evenly over chocolate.
Refrigerate until filling is set, at least 1 hour and up to 3 hours.
Dust with cocoa or top with chocolate shavings.
Slice with sharp knife and serve.
based on a recipe from America's Test Kitchen Cook's Country