Form pizza dough into two balls, one about 20 per cent larger than the other; cover and let rest.

In large pot of boiling salted water, blanch asparagus until tender-crisp; drain, chill under cold water and thoroughly drain. Chop into 1-inch/2.5 cm pieces.

With fork, stir together ricotta, egg, egg yolk, Parmesan cheese, chives, salt, nutmeg and pepper. Set aside.

On lightly floured surface, stretch or roll out large ball of dough into 14-inch/35 cm circle; with circle, line bottom of lightly-greased 12-inch/30 cm pie or pizza pan (or place on baking sheet). Top with prosciutto. Spread on ricotta mixture; lay asparagus on top. Cover with Gruyère cheese.

Roll out remaining dough into 12-inch/30 cm circle; centre over filling. Stretch and roll rim of bottom dough over edge of top dough, pinching together to seal. Cut a vent in centre. Brush with milk; sprinkle with fennel seeds. Bake in bottom third of 375 F/190 C oven until top is golden and filling is bubbling, 45 to 55 minutes.

Makes 8 to 12 servings.