Oatmeal Sandwich Cookies with Fluffy Vanilla Buttercream Frosting will make you weak in the knees they’re so good. I’m not kidding! They’re also very rich. So make the cookies tiny – about a tablespoon of dough per cookie – and you’ll end up with cookies that are two or three bites of heaven.
The moment I clicked through to Thalia’s blog post, I knew that I would have to make these cookies. If you haven’t visited Butter and Brioche, you must. Her recipes are creative and utterly reliable. Her recipe was for Oatmeal Sandwich Cookies with Smoked Treacle Buttercream. I’ll be honest, I’d never heard of Treacle, but discovered that it is the British term for molasses. Though her cookies sound perfect as is, I decided to riff on the recipe. I swapped in whole grain flour and stirred in walnuts instead of pecans because I happened to have them on hand. And for the sandwich filling, I went with fluffy vanilla buttercream frosting – my favorite.
When you make these, I recommend that you make them very small, just one or two bites. They are incredibly rich. I love this 1 tablespoon scoop, it’s perfect for scooping cookie dough and frosting for the middle.
This recipe makes about 25 little sandwich cookies. They make a great edible gift, party or holiday treat and they freeze well too!
- 2/3 cup unsalted butter at room temperature
- 1/2 cup granulated sugar
- 3/4 cup brown sugar packed
- 1 egg
- 1 tablespoon vanilla extract
- 1 tsp white vinegar
- ½ tsp salt
- 1 tsp baking powder
- ½ tsp baking soda
- 1 tbsp ground cinnamon
- 1 cup white whole wheat flour 120 g
- 2 ½ cups old-fashioned oats 240 g
- ½ cup chopped walnuts 75 g
- 1 recipe Fluffy Vanilla Buttercream Frosting
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Preheat oven to 350°F.
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Line a baking sheet with parchment paper.
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In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon and salt. Set aside.
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Add butter and sugars to the bowl of a stand mixer fitted with the paddle attachment. Beat at low speed until combined; increase speed and beat until fluffy, 2 to 3 minutes more. Add egg, vanilla and vinegar; beat well, scraping down sides of bowl as needed. Add flour mixture – cover mixer with a kitchen towel to protect your counters from a flour flurry. Start at low speed to stir, then increase to medium and mix until fully combined. Add rolled oats and walnuts; mix just until combined.
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Scoop dough into walnut sized balls (my favorite cookie scoop) and arrange about 2-inches apart on prepared baking sheet. Bake for 8 to 10 minutes, until golden brown on the edges and still soft in the middle. Let rest a few minutes on baking sheet before transferring to a cooling rack. Repeat process with remaining dough.
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Once the cookies have cooled, spread your desired amount of fluffy vanilla buttercream frosting on the bottom side of one cookie, and top with another.
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Welcome and thanks for being here! I'm Marissa, here with approachable and delicious real food recipes inspired by the seasons. 
I absolutely love Thalia’s blog! She posts the most amazing looking cakes and other sweets. Speaking of amazing, I’m thinking these cookies need to happen ASAP. I love oatmeal cookies, and I love vanilla buttercream…so this one combines 2 of my favorites. 🙂 I’ll take a baker’s dozen today, please!
These little cookie sandwiches look fantastic, Marissa! The combo of oats, walnuts, cinnamon, and slightly salter buttercream frosting makes the perfect treat. Well done!
Thank you, my friend!
These look amazing! Why aren’t you across the street from me so I can help you with the clean up? ?
I wish you lived across the street, Mary! xo
I love sandwich cookies cause it’s like two cookies for one 🙂 !! Oatmeal cookies are a favourite around here so I can definitely see these happening in our kitchen! Pinned! Happy Easter!
Yes! Hooray for two-cookies-for-one (and bonus buttercream)! Happy Easter to you!! xo
Thalia’s blog is absolutely BEAUTIFUL! Her photos are stunning and creations are just genius, right?! Love that she inspired these stellar sandos! I have a SERIOUS weakness for oatmeal sandwich cookies. Like, I can NOT be trusted around them, because I will eat them all. I’m not kidding! 😉 So you know I’m just dying over these, Marissa!!! They look fabulous and that vanilla buttercream looks dangerously delicious!! Gorgeous photos, my dear! I’m drooling! Pinned! Cheers! I hope you and your family have a beautiful Easter! <3
Aww…thank you, Cheyanne!! Hope you have a beautiful Easter too! xo
This looks so good!
Thanks, Kaisha!
These oatmeal sandwich cookies look amazing! Love that they’re filled with the amazing and very delectable vanilla buttercream! Yum- thanks for sharing your lovely recipe!
What a sweet note, thank you!
These look absolutely fabulous Marrisa (pinned)! I wanted to stop by today to wish you a Happy New Year! Here’s looking forward to wonderful things for you and your family in 2015!
Happy New Year, Kristi! xo
These look so delicious and your photos are gorgeous! I just took my first look at Thalia’s blog and I totally see what you mean!
Thank you, Sonali. She’s a talent, isn’t she!
Saw this of G+ community and had to stop in to say how incredibly gorgeous this is. Oatmeal Sandwich Cookies looks Stunningly delicious! 🙂
Hi, Anu! Thanks so much!
I love Thalia’s blog too! She is incredibly talented. Thank you for sharing these beautiful cookies – we’re having a small New Year’s Eve party and I’ve been thinking about what kind of cookies to make! 🙂
If you end up making them, I’d love to hear what you think! xx
Isn’t Thalia a legend?? I LOVE her blog, and you are so right, there is something “sexy” about it!! I love these! I must give it a go – I love the rustic, lumpy oatmeal with that rich smooth buttercream in it…..so bummed you don’t live closer, I just want to camp out at your dining table and eat all the amazing stuff you cook!
That makes two of us – I have a feeling that you and I could cook up some incredible feasts! 😉
I saw these on your IG and thought that they looked amazingly tempting! 😀
Thanks, Lorraine!
These cookies look beautiful and delicious! The vanilla bean buttercream sounds amazing! Definitely have to try them! Love Thalia’s blog and it is good to know how reliable her recipes are 🙂
Thank you, Lyubormira!
Yum!!! These look and sound amazing! I’m drooling just thinking of the buttercream! Pinned!
Thanks so much!
These look and sound incredible. I think I’ll add a little maple syrup to the buttercream and call it a day. Yum, looking forward to making these, thanks Marissa!
Love the idea of maple syrup, Kevin!
Marissa! These cookies look amazing!!! and I love Butter and Brioche. . definitely tagging this for later. . my goal in the new year is to try to eat a bit healthier with treats like this scattered throughout! 😛 happy NYE!
Thanks Alice! Happy NYE!!
Love your take on the cookies, Marissa! x
Thank you for the inspiration, Thalia!
YUMMM. Oatmeal sandwich cookies are the BEST cookies! Something about their hearty bite. 🙂
I agree, Carla!