Preheat the oven to 350°F (177°C). Grease a 12-cup Bundt pan thoroughly and dust with flour, or spray with floured cooking spray; set aside.
In a large bowl, combine the yellow cake mix, 3.4 oz box of pistachio pudding mix, eggs, club soda, vegetable or canola oil, and almond extract.
Beat the batter with a handheld electric mixer on low for about 30 seconds, then increase to high and beat until well blended and smooth, about 1–2 minutes.
Pour the batter into the prepared Bundt pan and smooth the top. Bake for 40–45 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Let the cake cool in the pan for 10–15 minutes, then invert onto a cake stand or platter and allow it to cool completely before frosting.
To make the frosting, whisk together the remaining 3.4 oz box of pistachio pudding mix and 3/4 cup cold cow's milk in a large bowl. Beat with a handheld mixer on medium-high until it begins to thicken, about 2–3 minutes.
Fold in the thawed whipped topping and beat briefly to combine, about 1–2 minutes, until the mixture is smooth and spreadable.
Spread the pistachio pudding frosting over the cooled cake, covering the top and sides as desired.
Sprinkle the shelled pistachios evenly over the frosted cake and serve immediately, or refrigerate until ready to serve.