To make pasta, sift the flour, semolina and 1/2 teaspoon of salt directly onto a work bench. In a small bowl, lightly whisk the eggs and water together and stir in the saffron infusion. Make a hollow in the centre of the flour and pour in the egg mixture. Gradually combine with your fingertips. Knead well for 5 minutes. The dough should be quite stiff. Cover with plastic wrap and leave to rest for 30 minutes.
Cut the dough into 4 pieces, flatten, sprinkle lightly with flour and pass through the rollers on the widest setting.
Adjust the rollers to the next smallest setting and pass the pasta sheets through again, dusting lightly with flour whenever sticky. Continue rolling the pasta through each setting until it is about 1mm thick.
Set aside to dry for 20 minutes or until dry to touch but still pliable and not brittle. With a pastry wheel or knife, cut the pasta into wide ribbons (20 cm long). The pasta can be cooked at this stage or left to dry further.
Fill a stock pot with water and 2 teaspoons of salt and bring to the boil. Meanwhile, preheat the oven to 200oC. Lay the prosciutto in a single layer on an oven tray lined with baking paper. Bake for 8-10 minutes, until it is just beginning to colour. Transfer to a wire rack or paper towel. The prosciutto will become crisper as it cools. Break into pieces.
Heat 1 tbs olive oil in a small pan and cook the spring onion gently for 2 minutes.
When the water is boiling, carefully drop in the pasta, stirring as you do so to prevent it sticking together. Cook for around 2 minutes. When the pasta is almost done, plunge in the asparagus and peas in the pot with the pasta to blanch. Cook for 1 minute or more until the vegetables are bright green and the pasta is ready.
Drain off the water and return the pasta and vegetables to the pot. Add the cooked spring onion , a drizzle of olive oil, salt and pepper and toss slightly.
Serve topped with prosciutto pieces and shaved Parmesan.