Step 1

Position a grill rack about 12cm from heat source and preheat grill. Brush the inside of a 7-cup (1.75L) baking dish with the butter. In a small bowl, mix the breadcrumbs, walnuts, extra butter and half the parmesan.

Step 2

In a large saucepan of boiling water, cook the pasta following packet directions or until al dente, adding the broccoli for the last 2 mins of cooking. Drain the pasta mixture, reserving 2/3 cup (160ml) of the cooking liquid.

Step 3

Return the pasta mixture to the pan with the cheddar and remaining parmesan, stirring until the cheese melts. In a medium bowl, whisk the ricotta with 1/3 cup (80ml) of the reserved cooking liquid. Add ricotta mixture to the pasta mixture in the pan and stir until well combined and saucy. Stir in the remaining cooking liquid, a little at the time, to loosen the sauce if necessary.

Step 4

Transfer the pasta mixture to the prepared baking dish and sprinkle with the breadcrumb mixture. Cook under the grill for 2-3 mins or until the breadcrumb mixture is golden brown. Serve immediately.