preheat oven to 375˚
sift the dry ingredients together for the whoopie pie
cream the sugar and vegetable oil together
beat on the eggs and vanilla until fluffy
mix the flour and buttermilk into the sugar mix
stir just to combine, scrape the bowl, and mix again
drop by Tablespoonfuls onto baking sheets
bake 5-6 minutes until the cookies spring back when poked but not hard or overbaked
when done let them rest a minute on the baking sheet and then remove to a baking rack to cool
make the filling by cooking the flour and milk together over medium heat until thick like pudding, don't overcook!
add the sugar and whisk to dissolve
cover with plastic wrap and let it cool
beat the butter in a stand mixer on medium for 2 minutes until it's fluffy
then with the mixer on medium add the cool flour mix by spoonsful until incorporated
the beat in the vanilla
switch to a whisk attachment and beat on medium until light, fluffy, and yet sturdy
match up your whoopie pie cakes and divide the filling between the pairs of pies
serve immediately