How to Make It
Make the icing. Beat the shortening, butter, and vanilla together in the bowl of a standing heavy-duty mixer with the paddle attachment on low speed until combined. Gradually beat in the confectioners’ sugar. Increase the mixer speed to medium-high and beat until fluffy, about 1 minute. Mix in the crushed cookies. Transfer to a bowl, cover, and store at room temperature for up to 1 day.
Make the pancake batter. Sift the flour, granulated sugar, baking powder, and salt together into a large bowl. Whisk the milk, buttermilk, eggs, unsalted butter, and vanilla together in another bowl. Pour into the flour mixture. Whisk just until combined. Stir in the crushed cookies.
Position a rack in the center of the oven and preheat the oven to 200°F. Heat a large griddle or two skillets over medium heat until a splash of water skitters on the surface. Lightly oil the griddle. Using about ⅓ cup for each pancake, pour the batter onto the griddle. Cook until bubbles appear on the pancake surface and the bubbles burst, about 2 minutes. Flip the pancakes and cook until the undersides are golden brown, about 1 minute more. Transfer to the oven rack to keep warm while cooking the remaining pancakes. If the batter thickens upon standing, thin with a little more milk.
Serve. Spread each pancake with a dollop of the icing. Stack the pancakes in tall stacks, and top each stack with additional icing and a generous sprinkle of crushed cookies and confectioners’ sugar, if desired. Serve immediately with the remaining icing passed on the side.