Vegetarian Sausage Roll with Caramelised Onion

A vegetarian take on the British sausage roll, this savoury pastry keeps the familiar crisp, golden puff pastry shell while replacing the meat with a hearty lentil and mushroom filling. Caramelised onions bring sweetness, Dijon adds gentle sharpness, and thyme gives the mixture a classic herby depth, helping it eat like a proper sausage-style centre rather than a loose vegetable filling. It works well warm from the oven, but is just as useful at room temperature, making it a strong option for lunches, picnics, packed boxes or a simple savoury snack.
Cuisine style British savoury baking
Flavor profile Buttery • Savoury • Herby
Techniques Sautéing • Baking • Pastry shaping
Key equipment Oven • Baking tray • Frying pan
Time commitment Under 1 hour
Cooking style Make-ahead friendly • Crowd-friendly

Why this recipe works

  • Crisp pastry, substantial filling: Flaky puff pastry contrasts with a cohesive lentil and mushroom centre that holds together well when sliced.
  • Deep savoury flavour: Browning the mushrooms first removes excess moisture and builds a meatier base, while caramelised onions add sweetness and depth.
  • Good warm or room temperature: The filling stays satisfying without needing a sauce, making the rolls useful for lunches, picnics and sharing plates.

Get the most out of this recipe

Texture tips

  • Keep the filling dry: Cook the mushrooms until their liquid has evaporated and the pan looks dry before mixing the filling.
  • Keep the pastry cool: If the pastry softens while shaping, chill the assembled roll briefly before baking so it puffs cleanly.

Common mistakes

  • Do not crowd the mushrooms: Crowding encourages steaming rather than browning, which can leave the filling wet and less savoury.
  • Bake until deeply golden: Pale pastry is often under-baked in the centre, so look for a puffed, crisp, deep golden finish.

Make-ahead tips

  • Prepare the filling ahead: The mushroom and lentil filling can be made in advance, cooled completely and kept chilled until you are ready to assemble.
  • Reheat for crispness: Reheat baked rolls on a tray at 180°C (355°F) until piping hot and crisp rather than using a microwave.
  • Freeze baked rolls: Cool the baked rolls fully before freezing, then reheat from frozen on a baking tray for the best pastry texture.

Ingredient notes

  • Choose good puff pastry: All-butter puff pastry gives the richest flavour and a more delicate flake, but any ready-rolled puff pastry can work.
  • Thyme options: Fresh thyme gives a brighter herbal note; dried thyme is stronger, so use it more sparingly.
  • Mustard balance: Dijon mustard sharpens the filling and balances the sweetness of the caramelised onions.

Equipment you'll need

Ingredients
Instructions
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  1. Heat the oven to 200°C (390°F) and line a baking tray with parchment paper. If the puff pastry is frozen, let it thaw until pliable but still cool.
  2. Finely chop the button mushrooms. Heat the olive oil in a frying pan over medium-high heat, then cook the mushrooms for 8 to 10 minutes until their liquid has evaporated and they are lightly browned.
  3. Tip the mushrooms into a mixing bowl and let them cool for 2 minutes. Add the canned lentils, caramelised onions, Dijon mustard, fresh thyme, breadcrumbs, black pepper and fine sea salt, then mash and mix until you have a cohesive, sausage-style filling.
  4. On a lightly floured surface, roll the puff pastry into a rectangle about 3 mm thick. Shape the filling into a long log down the centre, then bring the pastry over to enclose it and press to seal; place seam-side down on the tray.
  5. Beat the egg, then brush it over the pastry. Score the top lightly and cut into 8 pieces, spacing them slightly apart on the tray.
  6. Bake for 20 to 22 minutes until the pastry is puffed, crisp and deep golden. Rest for 5 minutes before serving warm or at room temperature.

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Recipe notes

Tips

  • For the best puff, keep the pastry cold; if it softens while shaping, chill the assembled roll on the tray for 10 minutes before baking.
  • Cook the mushrooms until the pan is dry and they are starting to brown, otherwise the filling can make the pastry soggy.
  • If serving to vulnerable groups, use eggs with a lion mark or another pasteurised equivalent.

Substitutions

  • Replace Dijon mustard with whole-grain mustard for a milder heat and a coarser texture.
  • Replace fresh thyme with dried thyme, using half the amount.

Storage

  • Refrigerate up to 3 days
  • Cool completely, then refrigerate in an airtight container. Reheat on a baking tray at 180°C (355°F) for 10 to 12 minutes until piping hot and crisp; freeze baked rolls for up to 2 months and reheat from frozen at 180°C (355°F) for 18 to 22 minutes.

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Recipe overview

  • Servings: 4 servings
  • Yield: sausage rolls
  • Total time: 55min (25min active)
  • Difficulty: Medium
  • Cuisine: British
  • Allergens:
    Eggs Gluten Wheat
Freezer friendly Kid friendly

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