Heat the olive oil and butter in a large frying pan, add the onion and garlic, cook gently until softened but not coloured. Add the rice and stir, cook for 1 minute.
Pour in the wine allowing it to evaporate, stir.
Add the hot stock a ladle at a time allowing it to be absorbed before adding more, while continuing to stir, it should take about 20-25 minutes to cook. The rice should be soft and creamy with a loose texture, add a little more stock or water if necessary.
While the risotto is cooking, blanch the asparagus and peas in boiling water for 2 minutes, drain and cover.
Stir in the Black Bomber cheese, half of the chopped mint, lemon zest and juice, and the asparagus and pea mix. Season to taste.
Serve immediately with a sprinkle of cheese and the remaining mint.