What to do with all that squash and what to serve on game day — two questions, one easy answer: this roasted squash sandwich. A simple, flavorful slider with roasted butternut (or any roasting squash), balsamic caramelized onions, and a spicy Sriracha mayo. It’s vegan-friendly, easy to scale, and perfect for casual gatherings.
We keep getting different squashes in our weekly farm box — some are easy to recognize, others look like green, bumpy pumpkins. If you’ve ever wondered how to handle a large, slippery squash when there’s no one around to help cut it up, here’s a foolproof approach: roast it whole.
To roast whole squash safely and easily: make a couple of small knife holes in the skin, rub a light coating of oil over the surface, place the squash on a baking sheet, and bake at a moderate temperature until the flesh is soft and a knife slips in without resistance. For butternut-sized squash that can take around 30–60 minutes depending on size and oven. Let it cool, cut it open, scoop out seeds, peel away the softened skin, cube the flesh, and refrigerate. You’ll have ready-to-use roasted squash for salads, sides, curries — and sandwiches.
For these sliders I tossed cubed roasted squash with a little olive oil, salt, pepper, and fresh herbs, layered it on toasted slider buns with lettuce and optional tomato, added sweet balsamic caramelized onions, and finished with a spicy Sriracha mayo. It’s messy, satisfying, and great for serving a crowd.
If you don’t want to roast a whole squash, you can pan-sear raw slices until tender or use store-bought roasted cubes. The method below keeps things flexible so you can adapt to what you have on hand.
These sliders work well as an appetizer or main, and they travel nicely for potlucks. The sweetness of roasted squash balances the tang of balsamic onions and the heat of the mayo, making each bite interesting without being complicated to prepare.
Assembly is quick: toast the buns, layer greens and squash, add caramelized onions, drizzle or spread Sriracha mayo, close the sliders, and dig in. Expect a bit of delicious mess — and that’s part of the fun.
Storage tip: roasted squash cubes keep well in an airtight container in the fridge for several days. Reheat briefly in a skillet to refresh their texture before assembling sandwiches, or use cold in salads if preferred.
Roasted Butternut Squash Slider with Balsamic Caramelized Onions and Sriracha Mayo — Vegan Sandwich Recipe
Prep: 15 mins • Cook: 20 mins • Total: 35 mins
Servings: 3 • Course: Burger • Cuisine: American
Ingredients
- Dinner rolls or slider buns
For the roasted squash:
- 2 cups cubed roasted butternut squash (or other roasting squash)
- 1 tsp extra virgin olive oil
- Salt, pepper, and Italian herbs to taste (fresh parsley optional)
For the Sriracha mayo:
- 1 Tbsp Sriracha or garlic chile sauce (adjust to taste)
- 4 Tbsp vegan mayo (or cashew/tofu-based mayo)
For the balsamic caramelized onions:
- 2 tsp oil
- 1 cup sliced onion
- 1/4 tsp sugar
- A generous pinch of salt
- 1 tsp balsamic vinegar (or more to taste)
Instructions
- Prep the buns or rolls. Toast lightly if desired.
- Top the bottom of each roll with lettuce or baby greens and tomato slices if using.
- Heat a pan with 1 tsp extra virgin olive oil. Toss the roasted squash cubes with salt, pepper, and herbs, then warm them in the pan for a minute. You can serve the squash cold if you prefer.
- If you don’t have pre-roasted squash: slice raw squash and cook in a greased pan over medium heat. Flip after 6–8 minutes, season, and cook until tender.
- Make the caramelized onions: add enough oil to coat a pan and heat over medium. Cook the sliced onions about 10 minutes, add a pinch of salt and 1/4 tsp sugar (for ~1/2 cup onion), and a few drops of water. Continue to cook on low-medium, stirring every 6–8 minutes, until the onions are golden and soft. If they stick, add a little water. For balsamic onions, stir in 1/2–1 tsp balsamic vinegar and cook another 2–3 minutes.
- Prepare the Sriracha mayo by mixing Sriracha (start with 1 Tbsp) into 4–5 Tbsp vegenaise or your preferred vegan mayo. Adjust heat to taste.
- Assemble sliders: place warmed squash on the roll, top with balsamic caramelized onions, and drizzle or spread Sriracha mayo. Close with the top half of the roll.
- Serve immediately and enjoy — expect a little delicious mess from the juicy, saucy filling.
Notes
Nutritional values below are an approximation per serving.
Nutrition
Calories: 229 kcal • Carbohydrates: 18 g • Protein: 1 g • Fat: 16 g • Saturated Fat: 1 g • Sodium: 426 mg • Potassium: 406 mg • Fiber: 2 g • Sugar: 4 g • Vitamin A: 9920 IU • Vitamin C: 26.8 mg • Calcium: 57 mg • Iron: 0.8 mg
