Preheat the oven to 220°C (425°F) (200°C/400°F fan-forced).

Place the cauliflower florets in a large microwave-safe container with ¼ cup (60 ml) of water. Cover with the lid slightly ajar. Microwave on high for 6–8 minutes or until easily pierced with a fork. If not tender, continue cooking in 2-minute intervals. The length of time depends on the strength of your microwave.

In a medium bowl, combine the cheddar, mozzarella and parmesan. Mix to combine, then set aside.

Heat the butter in a medium saucepan over low heat. Once melted, add the flour and stir for 1–2 minutes until well combined. Add the mustard powder and stir to combine.

Add ¼ cup (60 ml) of the milk, whisking until a thick paste forms. Once combined, gradually continue to add the remaining milk, whisking until smooth. Bring to a simmer and cook, whisking constantly for 4–6 minutes, or until the sauce begins to thicken and starts bubbling around the edge of the pan. Add the cream cheese and whisk until combined and smooth. Add the cheese mixture, reserving 1 cup for the topping. Add the salt and pepper and stir until the cheese is incorporated and melted.

Sprinkle the base of a baking dish (roughly 30 x 20 cm/12 x 8 inch base measurement) with the breadcrumbs. Place the cauliflower on top. Pour over the cheese sauce. Sprinkle the top with the reserved cheese. Place on a baking tray lined with baking (parchment) paper and place in the oven on the middle rack.

Bake for 25–30 minutes or until golden and bubbling on top.

Scatter the breadcrumbs on a separate baking tray lined with baking paper. Drizzle with olive oil and add the thyme and salt. Use your fingers to evenly distribute. Add the breadcrumbs to the top rack of the oven for the last 3 minutes of the cauliflower cooking time, or until golden brown. Note that once they are out of the oven, they will continue to brown.

Allow the cauliflower to rest for 5 minutes before serving.

Sprinkle the cauliflower bake with the thyme crumb and serve.