Stop struggling with soggy rhubarb flapjacks. This easy recipe solves the moisture problem, delivering a traditional chewy texture every time. By infusing the oats with a hint of ginger and using natural honey instead of golden syrup, these rhubarb and ginger flapjacks are the ultimate way to use up fresh garden rhubarb this spring.
While stewed rhubarb is a classic with custard, the real magic happens when you sandwich lightly stewed rhubarb chunks between layers of ginger-infused oat dough. This layering technique is the secret to the ultimate chewy flapjack, ensuring a tart, fruity centre without compromising the firm, buttery set of the oats.
This recipe works perfectly with pink forced rhubarb or seasonal garden rhubarb.
Ingredients and Possible Substitutions
This is just an overview of the ingredients I used to make this recipe, along with possible alternatives and why I may have used them. A complete list of ingredients and full instructions can be found in the Recipe Card below.
For the Rhubarb
Fresh Rhubarb - You can use frozen or tinned rhubarb, but they both produce excessive amounts of juice, which you should avoid using, to avoid soggy Flapjacks.
Honey - Runny or set/crystallised honey is ok.
For the Flapjacks
Butter - Unsalted
Soft brown sugar - I love using brown sugar; it gives a slight nutty flavour to all my baking.
Honey - Runny or set/crystallised honey is ok.
Pinch of salt - Try using crushed sea salt.
Ground ginger - my preferred option, added to the dry ingredients. But if you have a jar of crystallised ginger, grate a small piece before adding it to the stewed rhubarb instead of the dry ingredients.
Porridge Oats, not jumbo oats - If you only have jumbo oats, blitz them in a food processor for a few seconds to break them down a little.
Plain White Flour - All-purpose flour is fine.
Instructions
How to Cook Rhubarb for Flapjacks
It helps to stew the rhubarb a little before adding it between the two layers of unbaked dough. Don’t forget to add a little honey, not too much, to combat the tartness of the rhubarb.
Step 1: Clean the rhubarb stalks and peel if the skins are thick and tough. Chop into 1 inch chunks.
Step 2: Place the rhubarb in a shallow pan along with the honey and gently simmer until the rhubarb begins to soften, but do not overcook. Avoid stirring, or the rhubarb will become mushy. Take off the heat.
How to Make Rhubarb Flapjacks with Honey and Oats
Step 3: Preheat the oven to 180c fan oven. Grease and line an 8inch (20cm) by 8 inch (20cm) square tin with non-stick baking parchment for easy release.
Step 4: Melt the butter, sugar and honey in a small pan over a medium heat. Do not boil. Take off the heat.
Step 5: In a large mixing bowl, mix the flour, oats, salt and ground ginger. Make a well in the centre and pour in the melted liquid. Mix until well combined and all the oats are covered with melted butter.
Step 6: Spread half of the Flapjack mixture evenly and firmly into the base of the prepared tin.
Step 7: Arrange the stewed rhubarb over the Flapjack layer. TIP: Take care not to add too much of the residual rhubarb juices, or the Flapjacks will become too soggy.
Step 8: Spread the remaining Flapjack mixture evenly over the top of the stewed rhubarb. Pressing down gently.
Step 9: Bake in the centre of the oven for 25 minutes or until baked and golden on the top. Leave to cool for a few minutes before partially slicing. See next step.
Step 10: When the Flapjacks have cooled for a few minutes, use a serrated knife and partially slice into squares. TIP: This makes it much easier to slice into squares when the Flapjacks have cooled completely.
Step 11: When the Rhubarb and Ginger Flapjacks have cooled completely, use a large serrated knife to slice through the remaining layer. TIP: If you try to cut flapjacks when they are still warm, they will crumble and fall apart like cherry blossoms in a light breeze, and we don’t want that.
Eat on their own, with custard, or cream. For a slightly healthier option, serve with Greek yoghurt.
Storage
Room temperature or in the fridge. Flapjacks will keep for several days in a cool place, in an airtight container.
Try freezing in individual portions. Bring back to room temperature before serving. TIP: Be mindful that once the Flapjacks are thawed, the rhubarb layer could have a little more moisture due to the rhubarb being frozen. See the Q&A notes below.
Tips and FAQ
Tip 1: If you try to cut flapjacks when they are still warm, they will crumble and fall apart.
Tip 2: Partially slice the top layer of flapjacks before they start to cool. This makes it much easier to slice into squares when the Flapjacks have cooled completely.
Tip 3: Take care not to add too much of the stewed rhubarb juice, or the juice from frozen or tinned rhubarb, or the Flapjacks will become too soggy.
Tip 4: Do not overcook the rhubarb, or it will become mushy.
Why is my Rhubarb Flapjack soggy?
Rhubarb often releases a lot of moisture into baking. To avoid soggy Flapjacks, preheat or roast the rhubarb to soften a little and release excess moisture. This recipe includes flour, which also helps absorb any excess liquid.
Can I use Frozen Rhubarb for Flapjacks?
Yes, you can. But thawed rhubarb releases more liquid than fresh rhubarb, so ensure you drain as much liquid as possible, using a sieve, before adding it to the flapjack recipe.
Recipe Card
Recipe Notes:
Storage
Room temperature or in the fridge. Flapjacks will keep for several days in a cool place, in an airtight container.
Try freezing in individual portions. Bring back to room temperature before serving. TIP: Be mindful that once the Flapjacks are thawed, the rhubarb layer may have a little more moisture because the rhubarb was frozen. See the Q&A notes below.
Tips and FAQ
Tip 1: If you try to cut flapjacks when they are still warm, they will crumble and fall apart. Wait until they are completely cold
Tip 2: Partially slice the top layer of flapjacks before they start to cool. This makes it much easier to slice into squares when the Flapjacks have cooled completely.
Tip 3: Take care not to add too much of the stewed rhubarb juice, or the Flapjacks will become too soggy.
Tip 4: Do not overcook the rhubarb; it will become mushy.