Preheat the oven to 350ºF and line a standard loaf pan with parchment paper. Set aside.
Add the dry ingredients together in a bowl and stir to combine. Set aside.
Cream the butter, sugar, and vanilla in a separate large bowl until light and fluffy with an electric or stand mixer.
Add one egg to the creamed mixture at a time until incorporated.
Slowly add the dry ingredients to the wet ingredients. Mix with the electric mixture until incorporated. Slowly add the almond milk to the mixture until the batter is thick but pourable.
Pour the batter into the lined pan and sprinkle the chopped pistachios on the top of the loaf. Use a butter knife to create a line down the middle of the loaf. Bake for 50-60 minutes.*
Remove the loaf from the oven when the life comes out clean or almost clean. Let it rest in the pan for 5 minutes (it will continue to bake). Remove the loaf from the pan and let it rest and cool completely on a wire rack before frosting.
While the loaf is cooling, prepare the buttercream frosting. Heat a small skillet over medium heat and add the pistachios. Toast the pistachios for 4-5 minutes, toasting until golden, purple, and fragrant. Remove from the heat.
Transfer the pistachios to a small food processor, blender, or clean coffee grinder. Process the pistachios until they turn into a paste (similar to a nut butter). Set aside.
Use an electric or standing mixer and beat the butter, heavy cream and vanilla until light and fluffy. Slowly add the powdered sugar to the frosting and beat on low until smooth and combined.
Add 2-3 tablespoons of the pistachio paste to the frosting and mix on low until combined. The frosting will have bits of pistachio and may turn green depending on what type of pistachios are used. Option to add more pistachio paste here for a more pistachio flavor or color. Set aside extra pistachio paste for topping later.
When the loaf is cool, frost the top of the loaf and sprinkle any extra pistachio paste on top of the frosting. Enjoy.