These Portobello Mushroom Sandwiches are juicy, loaded with flavour and so easy to make!
Mushrooms shine when treated with a little care. A poorly prepared mushroom can be bland, but handled properly they become richly savory and satisfying. This recipe keeps the mushroom the star: garlic-butter roasted portobellos tucked into crisp ciabatta with hummus, caramelized onions, roasted red peppers and fresh greens. Read on for tips and the full recipe.
Garlic Butter Portobello Mushrooms
One of the simplest and most effective ways to prepare portobellos is to brush them with garlic butter and roast until tender. The butter helps the mushrooms caramelize and carry the garlic and parsley flavours through the sandwich.
Preparing Portobello Mushrooms
Remove dirt with a damp cloth or paper towel—do not rinse under water. Mushrooms hold a lot of moisture already and washing will make them soggy. You don’t need to remove the stalks; leaving them intact keeps more flavour and texture.
Garlic Butter
For the garlic butter mix melted unsalted butter with finely diced garlic, chopped parsley, salt and black pepper. Parsley is optional but it adds a fresh note that complements the garlic.
Can I use other mushrooms for this recipe?
Use mushrooms similar in size and shape to portobellos. In the UK, large flat mushrooms are a good substitute. Aim for mushrooms around 100g (3.5oz) each so they provide a hearty filling.
Process shots: melt butter, add parsley and garlic, brush mushrooms, bake.
Portobello Mushroom Sandwich
After testing a few combinations I settled on a filling balance that highlights the roasted mushroom while adding creaminess, sweetness and freshness:
- Hummus – Adds a creamy, nutty base that pairs beautifully with roasted mushrooms.
- Caramelized Onions – Sweet and mellow. If you’re short on time, thinly sliced raw red onion is an acceptable swap.
- Roasted Red Peppers – Use store-bought or homemade. If you prefer, substitute sliced tomato.
- Greens – A mix of spinach and rocket (arugula) gives peppery freshness, but any salad leaves work.
What bread to use?
Ciabatta is ideal: it crisps up nicely and contrasts with the soft mushroom. Other rolls can work—just be sure to toast them for texture.
Process shots: toast bread, spread hummus, add onions, add mushroom, add greens and pepper, top with bread.
Serving Portobello Sandwiches
Serve these sandwiches immediately while the mushroom is still warm and the garlic butter is soft. Making them ahead isn’t ideal because the mushrooms lose heat and the butter can firm up. Serve whole or slice in half to share.
- Crisp/Chip Recommendation: A roast chicken flavoured crisp pairs nicely here—the savoury mushroom and chicken-style seasoning complement each other.
- Side Recommendation: Sweet potato wedges or a roasted vegetable salad make great accompaniments.
Now onto the full recipe.
How to make a Portobello Mushroom Sandwich (Full Recipe)
Portobello Mushroom Sandwich
Equipment
- Large baking tray
- Small pot for garlic butter
- Sharp knife and chopping board
- Brush
Ingredients
Mushroom
- 4 large Portobello mushrooms (or large flat mushrooms ~100g each)
- 4 tbsp / 60g unsalted butter, melted
- 1 tbsp very finely diced parsley
- 2 cloves garlic, very finely diced then mashed
- 1/2 tsp salt
- 1/4 tsp black pepper
Sandwich
- 4 ciabatta rolls, halved and toasted
- 4 heaped tbsp hummus
- 1/3 cup caramelized onions (or quick-fried onion)
- 2 large roasted red peppers, sliced
- 4 pinches spinach/rocket or greens of choice
Instructions
- Garlic butter: Combine melted butter with parsley, garlic, salt and pepper in a small pot.
- Coat mushrooms: Place mushrooms stalk-side down on a baking tray. Brush the caps and undersides with the garlic butter.
- Bake mushrooms: Roast at 220°C / 450°F for 20–30 minutes, until fork tender. Remove any excess liquid if they pool too much.
- Assemble sandwich: Toast the ciabatta. Spread hummus on the bottom half, add caramelized onions, place the roasted mushroom on top, then add greens and roasted red pepper. Close the sandwich, press gently and serve warm.
Quick Demo
Notes
a) Ciabatta: Toasting adds a crunchy contrast to the soft mushroom. Toast halves in a hot dry pan or under the grill.
b) Caramelized onions: Use a slow-cooked caramelized onion recipe for best results. If short on time, lightly fry onions until golden or use raw red onion for a sharper bite.
c) Roasted red peppers: Store-bought jars work well—drain and pat dry. To char at home, roast until blackened, steam under cling film, then peel off skins. Swap tomatoes if preferred.
d) Nutrition: Calories and nutrition are estimates per sandwich and may vary based on ingredient brands and portion sizes.
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