Preheat the oven to 350° F. Combine the flour, baking powder, and salt in a medium bowl and set aside.
In a large bowl, whisk eggs, sugar, and vanilla until thick and pale-colored, 4 minutes. Add flour mixture to the egg mixture. Beat on low just until combined. Add buttermilk or milk and butter and mix to combine.
Pour batter into a parchment-lined 9 by 13-inch baking pan and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Cool on a wire rack, then cut into bite-sized squares, about 2 inches in diameter. Freeze squares of cake on parchment-lined baking sheet, covered with plastic wrap, until firm, about 2 hours and up to 2 months (if freezing for longer storage, wrap in foil after plastic wrap).
Make the Glaze and Dip
Whisk all glaze ingredients together in a large bowl until very thin and runny.
Using a dipping fork, dinner fork, chopsticks, or skewer, dip cake squares completely in glaze and tap on side of bowl to remove excess.
Immediately roll dipped cake squares in chopped peanuts and place on wire rack to set.
Cakes can be frozen with and without toppings for up to 2 months, well wrapped. Keep wrapped while thawing.