Put oven rack in middle position and preheat oven to 450°F.

Prepare a bowl of acidulated water (squeeze a lemon into some water). Halve apples and pears lengthwise, remove cores and place in bowl. Once you've finished them all, melt butter in a 12" heavy ovenproof skillet over moderate heat and sprinkle with sugar and spices. Arrange fruit halves, cut sides down, on sugar and cook, undisturbed, until sugar begins to caramelize, 3-5 minutes. Transfer skillet to oven and bake until tender, about 5-7 minutes.

Combine 1 cup heavy whipping cream, 1 cup whole milk, and 1/2 cup sugar in heavy medium saucepan. Bring mixture to simmer, stirring until sugar dissolves.

Whisk 3 large egg yolks and remaining 1/4 cup sugar in large heatproof bowl until blended. Gradually add hot cream mixture to yolk mixture and whisk until blended.

Return mixture to saucepan and stir over medium-low heat until custard thickens slightly and coats back of spoon when finger is drawn across and instant-read thermometer inserted into mixture registers 170°F, about 3 minutes (do not boil).Pour custard through strainer set over medium bowl. Place bowl with custard in larger bowl filled halfway with ice and water. Whisk occasionally until custard is almost cool to touch, about 5 minutes. Remove bowl with custard from ice water. Whisk yogurt and pinch of salt into custard. Refrigerate custard until well chilled.

Transfer custard to ice cream maker and process according to manufacturer's instructions. Transfer yogurt ice cream to freezer container. Cover and freeze until ice cream is firm. (Can be made up to 3 days ahead.)

While you are assembling the recipe, place a large (approx. 13x9) shallow metal pan and a fork in the freezer to chill.

Combine the water and honey in a large saucepan and stir over medium heat until honey is completely dissolved. Mix with fruit juices and orange flower water, and cool to room temperature.

When cool, pour into the metal pan. After 20-30 minutes in the freezer, use a fork to stir the granità, scraping it off the bottom and sides of the pan. Break up the frozen parts near the edges into smaller chunks and rake them toward the center. Do this every half hour or so, continuing to break up ice crystals until completely frozen, about 3 hours. If at any time the granita freezes too hard, simply leave it out at room temperature for a few minutes until it softens enough to be stirred again with a fork. Then return it to the freezer.

Check your granita mixture 20-30 minutes before serving to make sure that you can scoop the surface with a spoon. If it is too firm, let it stand at room temperature until serving time. To serve, scrape across the top of the frozen mixture with a large spoon. Granita is usually served in chilled footed dessert dishes, goblets, or wine glasses.

Oil a baking sheet and set aside. Cook sugar with salt in a dry 8" skillet over moderately high heat, undisturbed, until sugar begins to melt, about 5 minutes. Continue to cook, stirring occasionally with a fork, until sugar is melted into a deep golden caramel, about 3 minutes more. Remove from heat. Add walnuts, stirring with a heat-proof spatula to coat, then pour onto baking sheet and cool 10 minutes. Break nuts into smaller pieces, or finely chop, as desired.