In a medium saucepan, pour in 5½ cups of whole milk and heat over medium-high heat until steaming, then add almond flour and sugar, whisking continuously to combine. Once it reaches a gentle boil, reduce heat to low.

In a small bowl, measure out the remaining ½ cup of milk and whisk in cornstarch to create a smooth paste. Gradually pour this paste into the hot milk mixture while whisking quickly until thickened, about 5 to 10 minutes.

In a separate bowl, whisk the egg yolk until slightly frothy. Gradually add a cup of the hot pudding mixture to temper the yolk, then return to the saucepan and stir to combine.

Remove from heat and stir in vanilla extract, almond extract, and a pinch of salt. Ensure everything is well mixed.

Pour the creamy pudding into serving bowls or a large dish. Cool to room temperature, then refrigerate for at least 2 hours to set.

Before serving, sprinkle ground pistachios or sliced almonds on top as a garnish.