In a heavy saucepan over medium-high heat, combine the sugar with 1/3 cup water. Cover and bring to a boil. Uncover the pan and cook until the sugar turns golden amber in color and forms a caramel, 8–12 minutes. Be careful, as the caramel is very hot.
Combine the cream and milk in a large saucepan over medium-high heat and warm until small bubbles appear at the edges of the pan. Remove from the heat.
Preheat an oven to 325 F. Add 1/4 cup cool water to the caramel and whisk vigorously until the bubbles subside. Pour the caramel into the hot cream mixture and whisk together until mixed. Let cool for about 10 minutes.
In a bowl, whisk the egg yolks until smooth. Slowly add the caramel mixture, stirring constantly until mixed. Strain through a fine-mesh sieve into a glass measuring cup.
Have ready a kettle full of boiling water. Pour the custard into six 2/3-cup ramekins. Place the ramekins in a baking pan and place the pan on the oven shelf. Carefully pour the boiling water into the baking pan to reach about 1 inch up the sides of the ramekins. Bake until the edges of the custards are set, 40–50 minutes. Remove the baking pan from the oven and transfer to a rack to cool for about 10 minutes.
Carefully remove the custards from the water bath and let cool. Refrigerate for several hours or for up to overnight until well chilled. Garnish each with a dollop of créme fraîche, sprinkle with the cinnamon, and serve chilled or at room temperature.