Preheat the oven to 375 degrees. Spray bundt pan with nonstick spay well. Sprinkle with flour and coat the inside of the bundt pan. Tap it into all the little nooks and cranies. This will make it easier for the cake to release. (I usually do this over the sink as it can get messy!)
Chop the pistachios, set aside.
Make the cake according to the package directions using the cake mix, pistachio pudding, water, and milk. Beat until combined. Add the eggs one at a time, mix until combined. Beat until light and fluffy about 2-3 minutes.
Add half the pistachios into the cake batter, stir to combine.
Pour the batter into the prepared cake pan, and spread evenly. Tap the cake pan on the counter, this will release any air pockets in the batter. Place in the preheated oven. Bake for 45-50 minutes.
Remove from the oven. Place it on a cookie sheet for 10 minutes. After 10 minutes, invert it onto a cake stand or plate and allow it to cool completely.
Now it's time to make the frosting! In a stand mixer beat the cream cheese and butter until it's light and fluffy (about two minutes). Add the powdered sugar, vanilla extract and 1 tablespoon of the cream. Mix on medium until it begins to come together. Add additional cream as needed.
When the cake is completely cooled, it's time to decorate! If you want to make this look like an Everything Bundt Pistachio Cake, add the frosting to a piping bag with a 1A tip (the tip with the large circular hole).
Starting on the outside and working in, pipe a line of frosting from the bottom to the inside of the cake. Go to the opposite side of the cake and repeat. Continue piping the frosting on the cake until you've gone all the way around it.
Using an offset spatula, smooth out the icing on the inside ring of the cake. Top with remaining pistachios.