Process flour, salt, milk and eggs until smooth. Cover. Set aside for 20 minutes.
Spray an 18cm (base) non-stick frying pan with oil and heat over medium heat.
Pour 1/4 cup batter into pan and swirl to cover base. Cook for 2 minutes or until light golden. Turn. Cook for 30 seconds. Transfer to a plate. Cover to keep warm.
Repeat with remaining mixture to make 8 pancakes.
For the filling
Melt butter in a frying pan over medium-high heat.
Add mushrooms, garlic and onion. Cook, stirring, for 2 minutes or until mushrooms are tender. Transfer to a bowl. Cool for 10 minutes.
Stir in chicken, parsley and ricotta.
Putting the together the chicken pancake
Preheat oven to 200°C/ 180°C fan-forced.
Place 1 pancake on a plate and top with 1/4 cup filling. Roll up to enclose.
Place in a greased 8cm-deep, 20cm x 30cm ovenproof dish. Repeat with remaining pancakes and filling.
Top with passata and cheese.
Cover dish with foil. Bake for 20 minutes or until heated through. Remove foil. Bake for 5 minutes or until cheese is golden.