1 cup (240 milliliters) freshly brewed espresso (or substitute with freshly brewed coffee)
4 egg yolks
3/4 cup (180 milliliters) sugar
Thick whipped cream, for topping
Cocoa powder, for dusting
Small mason jars
Preheat oven to 300 F (150 C).
Heat milk and heavy cream in a saucepan until it just starts to steam. Remove from heat and whisk in freshly brewed espresso.
Whisk together egg yolks, eggs, and sugar. Pour half of the cream mixture into the yolk and sugar, whisking briskly to combine. Now pour the yolk and cream mixture back into the pot with the remaining cream mixture, whisking continuously until combined. Carefully pour custard mixture into eight small mason jars.
Place mason jars in a large casserole dish and fill the dish with about 2.5 centimeters of boiling water. Cover with tin foil. Transfer casserole dish to oven and bake for 90 minutes or until puddings have set with a slight crust around the edges.
Remove the casserole dish from the oven, carefully remove the mason jars, and let cool. Transfer mason jars to refrigerator to chill completely.
Top with tufts of thick whipped cream and dust with cocoa powder.