In a medium saucepan, heat the powdered butter and ½ cup powdered buttermilk over medium. Cook, whisking constantly to keep from scorching and turning down burner if needed, until browned and fragrant, about 6 minutes. Transfer to a large bowl and let cool slightly.

Add remaining ½ cup powdered buttermilk, flour, sugar, baking powder, and salt to the bowl and whisk together. This is your pancake mix; store at room temperature in an airtight container until ready to use.

For each batch of pancakes, measure pancake mix into a large bowl. In a medium bowl, beat eggs until smooth. Add seltzer and whisk to combine. Add the wet mixture to the dry and whisk to just combine.

Heat a large nonstick pan over medium; use a paper towel to rub the surface with a bit of vegetable oil. Working in batches, scoop the pancake batter into the pan using a ¼ cup measure. Cook the pancakes until browned and the bubbles across the surface have popped, about 2 minutes. Flip the pancakes and cook until set through, 1–2 minutes. Continue with the remainder of the batter, adjusting the heat to keep it at medium and re-oiling the pan surface as needed.