Preheat oven to 300 degrees F. Line a baking sheet with parchment paper or a silicone baking mat.
In the bowl of a stand mixer, whisk to combine flour, cornstarch, salt, and brown sugar. Add melted butter and vanilla and mix on low speed until a crumbly dough is formed. Add mini chips and stir until evenly distributed. Dough will appear dry and crumbly, but should stick together when squeezed.
Slightly knead dough to bring it together into some larger pieces, then crumble in a single layer on prepared baking sheet. Aim for various sizes, from pea-sized to marble-sized; break any larger pieces into smaller chunks. Bake for 15 minutes or until bottoms are lightly golden brown. Remove from oven and let cool completely.
Meanwhile, place most of your chopped chocolate (reserve a few large chunks for later) in a double boiler or a heat-proof bowl set over a pot of barely simmering water. Let it melt fully, stirring occasionally, until the temperature reaches 115-120 degrees F.
Remove chocolate from heat, setting it on a kitchen towel to stabilize and absorb the water. Gently stir until chocolate cools to approximately 80 to 84 degrees F.
Drop in the reserved large chunks of chocolate (ensure they show no signs of bloom or streaks), stirring gently but consistently. Return to the double boiler or ‘warm’ setting until chocolate reaches 88 to 91 degrees F, no higher.
Remove any remaining chunks of solid chocolate. Pour tempered chocolate onto a parchment or silicone-mat-lined baking sheet, spreading into an even layer using an offset spatula. Working quickly, sprinkle with chocolate crumbles, extra mini chocolate chips, and edible glitter as desired.
Set pan in a cool place until completely set. If your chocolate is not tempered, refrigerate the bark for about 30 minutes until firm. Break or cut the bark into bite-sized pieces.