Magnolia Bakery Banana Pudding

Pour 650 ml milk into a saucepan and heat over medium heat until warm.
In a large mixing bowl, whisk 4 egg yolks with 125 g sugar until well combined. In a small bowl, mix 50 g cornstarch with a splash of the warm milk until smooth, then whisk it into the egg mixture along with 2 tsp vanilla extract until fully blended.
Remove the warm milk from the heat and gradually pour it into the egg mixture, whisking constantly. Pour everything back into the saucepan and cook over low-medium heat for about 8 minutes, whisking regularly, until the mixture bubbles throughout and thickens to a creamy pudding.
Remove from the heat, add 30 g butter, and whisk until smooth. Transfer the pudding to a bowl, let it cool to lukewarm, then cover with plastic wrap touching the surface and refrigerate until fully chilled.
In a separate bowl, beat 350 g heavy whipping cream with 2 tbsp powdered sugar for about 4 minutes, until slightly thickened. Remove the chilled pudding from the fridge, whisk it until smooth, then gently fold in the whipped cream until fully incorporated with no streaks remaining.
Slice 3 bananas and layer the pudding mixture in serving glasses or a dish with the banana slices, 4 ginger cookies, crushed, and 50 g walnuts. Repeat the layers and finish with chopped walnuts on top.