01 - Combine pistachios and water in a bowl. Allow to soak overnight or for at least 6 hours. Drain and rinse thoroughly.
02 - Transfer soaked pistachios to a blender. Add 3 cups filtered water, vanilla extract, maple syrup or honey, and a pinch of sea salt. Blend until completely smooth.
03 - Pour mixture through a nut milk bag or fine mesh sieve into a pitcher, separating the liquid from the solids. Discard or reserve the solids for baking.
04 - Pour pistachio milk into a saucepan. Warm gently over medium heat, whisking continuously until hot but not boiling. Add sweetener if desired.
05 - Brew espresso or strong coffee using an espresso machine or coffee maker.
06 - Divide hot pistachio milk between cups, reserving some froth. Add espresso to each cup and stir gently to combine.
07 - Spoon reserved froth on top. Garnish with crushed pistachios if desired. Serve immediately.