Bring a large pot of water to a boil. Preheat your oven to 300 degrees F and place 6 ramekins inside a baking dish. Set aside.
In a medium bowl, whisk together the egg yolks. Set aside.
Combine the heavy cream, sugar and lemon zest in a large saucepan over medium heat. Bring the mixture to a simmer, stirring constantly until the sugar dissolves. Continue to simmer for about 5 minutes, stirring frequently. Reduce the heat to low.
Very slowly add the cream mixture to the egg yolks, whisking vigorously. Once about 1/2 of the cream mixture has been added to the egg yolks, transfer it all back to the saucepan. Whisk continuously just until the mixture is blended. Stir in the lemon juice. Remove from heat and pour the cream into the prepared ramekins. Pour the boiling water very carefully into the baking dish, until the ramekins are halfway submerged. Cover the baking dish with foil and place it in the oven to bake for 30 minutes, or until the pots de creme are just set.
Remove from heat and let cool for about 30 minutes before transferring them to the refrigerator to chill for at least 8 hours before serving.
When you go to serve, garnish the lemon pots de creme with blueberries and cookie crumbles. Best served after the pots de creme has set at room temperature for about 20 minutes after pulling them from the fridge.