Whoopie pies are a soft chocolate cake-like sandwich cookie filled with a smooth and creamy old-fashioned boiled milk frosting. These cookies are actually easy to make; both the cookies and frosting can be made in advance, making for an easy assembly.
About Whoopie Pies
Whoopie pies with boiled milk frosting are not actually pies; they are a soft cake-like sandwich cookie that started to become popular in the 1920’s. There is a debate on where they originated – they have both Pennsylvania Dutch and Maine origins. There is not a lot of information on where the name Whoopie Pie came from, but there are some recipes that also refer to these as “gobs.”
The traditional flavor is chocolate, but they have evolved into other flavors such as pumpkin or red velvet. These cookies are usually sandwiched with a smooth and creamy frosting, like as an old-fashioned boiled milk frosting, marshmallow crème or fluffy meringue frosting.
About this Recipe
My traditional chocolate version has Maine roots; the recipe originated from a cousin’s wife in the family who hailed from Maine, but lived in the Midwest. These whoopie pies contain an ingredient that was popular in farmhouse kitchens – sour milk. See tips below on how to make your own sour milk or you can substitute buttermilk.
This recipe also uses vegetable oil to achieve a moist cookie and results in a batter that is a little thicker than cake, but thinner than a cookie. Using a cookie scoop results in a more uniform-sized cookie, making them easier to sandwich together. I use a small cookie scoop to achieve this.
The Whoopie Pies are paired with an old-fashioned boiled milk frosting, which is a frosting that starts with cooking milk, sugar and flour until it is thick like a roux. Once it has cooled, it is then whipped with butter and vanilla until it is light and fluffy. It is actually the original frosting for red velvet cake and since it is less sweet than a traditional buttercream, it pairs well with the sweet chocolate cookies to make the whoopie pies.
See the storage tips below as both the cookie and frosting can be made in advance, making for an easy assembly.
Tips for Whoopie Pies with Boiled Milk Frosting
- To make sour milk for this recipe: add 1 tsp of white vinegar to the milk. You can also substitute buttermilk.
- Creating evenly sized cookies is essential to creating a uniform sandwich cookie. Use a small cookie scoop to achieve this.
- Piping the frosting onto the cookies allows for a cleaner looking cookie; you can also use an off-set spatula to spread the frosting.
- When making the frosting, the flour mixture should be completely cooled to room temp prior to whipping with the butter.
- Alternately if your butter is too soft, the consistency of this frosting will also be too soft.
- Both the cookies and frosting can be made in advance.
- Do not allow the cookies to touch when stored, as they will stick together. Store refrigerated up to 72 hours or freeze up to 3 months in an airtight container.
- The frosting will keep refrigerated for up to 5 days.
- The frosting will freezes well up to 3 months. To use from frozen; allow to thaw in the refrigerator. Once thawed, allow to come to room temperature and then whip to a light consistency.
Whoopie Pies with Boiled Milk Frosting
- cookie sheets
- parchment paper or silicone baking mats
- medium-sized cookie scoop
- piping bag, plastic baggie or off-set spatula
- small saucepan
- mixing bowls of various sizes
For the Cookies
- 3/4 cup granulated sugar
- 1/4 cup vegetable oil
- 1 large egg, room temperature
- 1/4 cup sour milk (see notes), or buttermilk
- 1/4 cup cocoa powder
- 1/4 cup hot water, heated to at least 110°F
- 1/2 tsp vanilla extract
- 1/2 tsp baking soda
- 1/2 tsp baking powder
- 1/2 tsp salt
- 1 1/3 cup all-purpose flour
For the Boiled Milk Frosting
- 3 tbsp all-purpose flour
- 3/4 cup milk, 2% or whole
- 1 cup granulated sugar
- 3/4 cup butter, softened
- 1 tsp vanilla extract
For the Cookies
- Preheat oven to 375°F and line cookie sheets with parchment paper or silicone baking mats.
- Combine sugar and oil in bowl of a mixer, mix until just combined.
- Add egg and mix until just combined.
- In small bowl, whisk cocoa until there are no lumps. Slowly pour in hot water and stir until cocoa is dissolved.
- Slowly add the dissolved cocoa to creamed mixture.
- Add in vanilla.
- Sift or whisk remaining dry ingredients in medium-sized bowl.
- Alternate adding the dry ingredients and the sour milk, beginning and ending with the dry ingredients.
- Using a medium-sized cookie scoop, scoop dough onto lined baking sheets about 2 inches apart, carefully forming uniform sized circles.
- Bake for 7-9 minutes, or until the tops of each cookie are just set (they should not jiggle when pan is moved).
- Remove from oven and allow to cool on baking sheets 1-2 minutes. Then, carefully move to a wire baking rack or parchment lined flat surface to cool completely.
- Frost when completely cool.
For the Boiled Milk Frosting
- In small saucepan, whisk milk, flour and sugar.
- Whisk over medium heat until thickened (almost as thick as a pudding).
- Immediately remove from heat and pour into a bowl. Allow to cool at room temperature.
- In large mixing bowl, whip softened butter until light, about 2 minutes.
- Add cooled flour mixture and whip on high speed, until light and fluffy.
- Add in vanilla extract.
- To pipe frosting between two cookies: pour frosting into a piping bag (or baggie). Snip the tip of the bag and slowly pipe the frosting onto the bottom of one cookie, top with the bottom of another cookie, "sandwiching" them together.
- Alternately, use an offset spatula instead of a piping bag to frost the bottom of one cookie and top with the bottom of another cookie, "sandwiching" them together.
- To make sour milk, add 1 tsp. of white vinegar to milk. You can substitute buttermilk instead.
- Boiled milk frosting can be made ahead of time, up to 48 hours. Store chilled. When ready to assemble whoopie pies, bring to room temperature and re-whip.
- Assembled whoopie pies will keep up to 72 hours when stored chilled, in an airtight container.