Mary Berry Thomas Flan

I made this on a sticky Wednesday afternoon when the oven just wasn’t happening, and to be honest, I wasn’t expecting much. Condensed milk and lemon sounded like it might lean a bit too sweet or soupy. But oh my word—I was wrong. The filling set like a dream without any gelatin or faff, and the lemon gave it a proper zing that cut through the richness beautifully.

The crust, though? Total drama. First go, it crumbled like a sandcastle. Pressing it too loosely meant it didn’t hold when I sliced. Let me show you how I fixed that, and what makes this no-bake wonder worth keeping in your back pocket for summer lunches, birthdays, or just because.

WHY THIS ONE WORKS SO WELL

This is one of those deceptively simple bakes that hits all the right notes: creamy, bright, and utterly stress-free.

• The lemon juice does all the setting work—no gelatine or eggs needed.
• Condensed milk + cream creates that velvety, mousse-like texture.
• And most recipes don’t bother pressing the crust up the sides—but Mary’s version does, and it makes the whole thing hold better when you slice.

INGREDIENTS + WHY THEY MATTER

• Condensed Milk (397g) – Thickens with lemon juice to create a lush, creamy base. I once tried light condensed milk and… nope. It never set properly.
• Heavy Cream (120ml) – Softens the sweetness of the milk and gives body. I’ve tried single cream—it’s too runny.
• Fresh Lemons (2) – The acid sets the filling and adds zing. Bottled juice tasted a bit… sad.
• Graham Crackers or Digestives (125g) – Digestives give a nuttier base; grahams are sweeter. Both work.
• Butter (85g) – Binds the base. Too little and it crumbles. I tried with 70g once—don’t.

MAKING IT YOURS (WITHOUT RUINING IT)

• Gluten-free? I’ve made this with GF digestive biscuits—turned out lovely. Just chill that crust extra long (I did 45 mins).
• No dairy? Haven’t found a full swap that sets the same, but Oatly whippable cream + coconut condensed milk came close. Bit softer, but tasty.
• Fruit swaps – Top with strawberries, raspberries, mango… even thin kiwi slices worked. Bananas made it a bit mushy next day.

MISTAKES I’VE MADE (AND HOW TO AVOID THEM)

What Went Wrong	Why It Happens	How to Fix It
Filling stayed runny	Used low-fat condensed milk	Stick to full-fat—it’s the setting magic
Crust crumbled	Didn’t chill long enough	Chill at least 30 minutes, or even freeze 10 mins
Lemon overpowered	Used 3 big lemons	Stick to 2 medium ones—zest and juice only

HOW TO MAKE MARY BERRY’S THOMAS FLAN

1. Line your tin – Use a springform or loose-bottomed 20cm tin. Line base + sides with parchment. Trust me, you’ll thank yourself later.
2. Make the crust – Melt butter, stir in crushed biscuits. Press firmly into base and up the sides. Chill for 30 mins minimum.
3. Mix the filling – Combine condensed milk, cream, lemon zest and juice. Beat until slightly thickened. (Mine took about 2 mins with a hand mixer.)
4. Pour + chill – Pour into crust, level it out, and chill for at least 4 hours. I left mine overnight—perfect.
5. Decorate – Add fruit just before serving. I used strawberries, blueberries, and a few mint leaves.

TIPS FROM MY KITCHEN

• I always zest the lemons straight over the bowl—less waste and more oil.
• I freeze the crust for 10 mins instead of just chilling. Holds better.
• If you want clean slices, dip your knife in hot water first.

STORAGE + SERVING

• Fridge: Keeps beautifully for 3 days, covered.
• Freezer: Wouldn’t bother. Tried it once—filling turned icy and sad.
• Serve with: Berries, mint, a dollop of whipped cream, or even a light elderflower cordial on the side.

FAQs

Q: Why is it called a Thomas Flan?
A: No official story, but Mary included it in Fast Cakes—could be named after a family friend or a test kitchen hit.

Q: Can I use lime instead of lemon?
A: You can! I’ve made it with lime zest + juice—more tropical, but just as firm.

Q: Why didn’t my flan set?
A: Usually it’s one of two things: using low-fat condensed milk, or not enough lemon juice. Or both.

Q: Do I need to whip the cream first?
A: Nope—just pour it in and mix. The lemon thickens everything naturally.

Q: Can I make this in advance?
A: Yes! Best made the day before—gives it time to fully set and chill.

Try More Recipes:

• Mary Berry Gin and Lime Drizzle Traybake
• Mary Berry Ginger and Orange Polenta Cake
• Mary Berry Glorious Chocolate Truffle Dessert
• Mary Berry Glazed French Peach Tart