Gather and prepare your ingredients. Preheat the oven to 200°C/180°C fan.
Bring a pot of water to the boil and add a generous pinch of salt. Add the broccoli and cook for 2-3 minutes, until tender and bright green. Remove, using a slotted spoon, and cool down immediately by either placing into an ice bath or running under a cold tap and placing into the fridge. Once cool, chop into smaller florets.Cooling down the broccoli as soon as possible helps to preserve its bright green colour and prevents over cooking.
Once the broccoli is done, bring the water back to the boil. Add the pasta and cook until al dente. Drain.Refer to package instructions for timing which will vary based on the shape you have chosen.
To make the bechamel sauce, place the oat milk into a saucepan with the onion, peppercorns, bay leaf and pinch of nutmeg. Heat for 4-5 minutes, until it reaches the shiver stage (how it gently moves before it begins to simmer). Pour into a jug and set aside to infuse while you make the roux.
Place the pan back over the heat. Add the olive oil and plain flour. Whisk for 2-3 minutes, until thickened. Then strain the oat milk back into the saucepan in 3-4 additions, whisking constantly to avoid lumps. The mixture should be thick enough to coat the back of a spoon. Add the nutritional yeast and mustard and stir to combine. Adjust seasoning to taste.
To make the pesto, place all ingredients into a blender and process until smooth. Add salt and pepper to taste.Add a splash of water to help it blend if needed.
Place the cooked broccoli into a bowl with the peas, edamame and cooked pasta. Pour over the pesto and toss to coat.There’s no need to pre-cook the peas or edamame.
Pour the vegetables and pasta into a 20x18x5cm baking dish. Pour over the bechamel sauce. Toss the breadcrumbs with the olive oil and sprinkle on top.
Place into the preheated oven and bake for 30 minutes until golden and bubbling. Allow to cool slightly before serving.