Infuse the cream. In a medium saucepan over medium heat, combine the heavy cream and granulated sugar. Add the medium-coarse ground dark roast coffee. Cook, stirring frequently, until steam just begins to rise and small bubbles form at the edges — about 4 to 5 minutes. Remove from heat. French press method (preferred): pour the hot cream mixture directly into your French press carafe. Steep for 10 minutes with the plunger up, then press slowly and deliberately. Pour the pressed cream through a fine-mesh sieve — press method first, then sieve — for the cleanest possible custard. Run it through the sieve a second time if you want absolute certainty. No French press: steep in the saucepan for 10 minutes, then strain twice through the fine-mesh sieve.

Prepare the egg base. In a mixing bowl, beat the egg yolks, vanilla extract, and fine sea salt together until the mixture is smooth and slightly lighter in color. Add the pinch of cinnamon and stir to combine.

Temper the yolks. Slowly pour the warm espresso cream into the yolk mixture in a thin, steady stream while stirring constantly. Rushing this step will scramble the yolks. Take your time.

Strain. If using the French press method, pour the pressed cream through a fine-mesh sieve. If steeping directly in the saucepan, strain the cream through the fine-mesh sieve — then strain it a second time. Two passes guarantees a custard with no detectable grounds. Divide the strained custard evenly among four 7-ounce ramekins.

Set up the water bath. Preheat your oven to 300°F. Line a baking pan that is at least 3 inches deep with a clean kitchen towel — this cushions the ramekins and prevents them from sliding. Place the ramekins in the pan. Pour hot water into the pan until it reaches halfway up the sides of the ramekins. Cover loosely with foil.