Preheat the oven to 325. On a parchment paper lined baking sheet, set the mini tart shells slightly spaced apart.
Take a small knife with a serrated edge in your hand, as though paring a small fruit, and cut along the top of the fat end of the egg shell, to remove it like a top. The egg will easily pop out into the tart shell.
Cut a small piece of cooked bacon and set it in the edge of the shell in the egg whites, taking care not to pop the egg yolk. Salt and pepper to taste.
Bake until the egg yolk is firm, about 10 minutes. Serve.
Once cooked, the tart is good to sit out room temperature for about an hour. If there are any leftover, simply wrap with cling film, keep in the fridge, and rewarm at a later time.