Chess pie and buttermilk pie are very similar but while chess pie is typically thickened with cornmeal, buttermilk pie is not. Buttermilk pie is a sweet and tangy dairy-based pie thickened with flour with lemon juice and/or zest added for more tanginess. Chess pie is a very sweet custard pie that sometimes has a small amount of milk added and maybe a little vinegar to tame the sweetness.