Add the feta to the centre of a large oven-safe pan and drizzle over 1 tbsp oil. Place in the oven at 200C/390F for 8 minutes.
Take it out and scatter the asparagus and tomatoes around it. Drizzle them with 2 tbsp oil and sprinkle with a pinch of black pepper. Place everything back in the oven for another 12-15 minutes or until the feta turns golden around the edges and is very soft right through the centre. The tomatoes should have softened and wilted a little, with the asparagus fork tender.
When you put the feta back in the oven, add the orzo to a large pot of salted water and cook until al dente. Drain in a sieve over a large bowl to collect all of the excess starchy water.
Use a fork to mash the feta until smooth, then stir in the orzo until everything is combined. Stir in the spinach and ½ cup of the starchy water until the spinach wilts and you've created a smooth and creamy sauce. You can toss in more starchy water a splash at a time if you need to.
To finish, stir through basil, chives and 2 heaped tbsp mascarpone, then check for seasoning and adjust if needed. Go easy with the salt, but black pepper is encouraged. Serve up and enjoy!