Heat up about a tablespoon of olive oil in a wide heavy pan. Make a slit down the side of each sausage and squeeze the sausage meat into the pan. Cook for about 10 minutes, continually breaking up the meat with a wooden spoon.
Add the fennel, fennel seeds and rosemary and cook for about another 5 minutes, stirring.
Pour in the wine, passata and about 1 cup/200 ml water, then leave to simmer gently for about an hour. Add salt and pepper to taste.
For the pizza
Pour the water into a large bowl and empty the packet of yeast into it. Leave for a couple of minutes to allow the yeast to dissolve.
Add the flour, oil, salt and sugar and combine with a knife or wooden spoon. Bring together the dough with your hands and knead for a minute or two until elastic.
Leave the dough to rise in a warm place for at least a couple of hours, then knead it again briefly to knock out some of the air.
Divide into 5 equal-sized balls of dough. Freeze any you don't want to use immediately at this point. (I wrap each ball tightly in plastic wrap and put in a ziplock bag.) Leave the dough balls you do want to use immediately to rest for half an hour.
Pre-heat your oven to hot (I set mine to 480F/250C). Stretch or roll out the dough pretty thinly (stretching is better but I can never do this!) and put onto a pizza stone or pizza or baking tray (pre-heat for best results), fairly quickly add your ragu topping and cheese and bake for about 10 minutes or until nicely browned and crisp.
Top with your chives or other greens just before serving.
Notes
I enjoyed this ragu sauce with pappardelle pasta one night and then made a pizza with it the second. Try it - it's delicious both ways! I used Sally's pizza dough recipe from Sally's Baking Addiction and it worked really well. Sally has some great tips in her post, too!