Place the chopped pears into a large nonstick saucepan on medium-high heat and cook the peas for30-45 minutes until they cook down into a thick jam-like sauce. Let the pears cool slightly, then add them to a blender and puree them into a smooth sauce.
Place the half and half, heavy cream, cinnamon stick, and rosemary sprig into a saucepot and cook the cream mixture on medium-low for 5-6 minutes until small bubbles appear around the perimeter of the pot (this is called scalding milk). Cover the cream mixture with a lid and allow it to steep for a few minutes.
Meanwhile, add the egg yolks and sugar into a bowl and beat well with a whish until it is a pale yellow color. Remove the cinnamon and rosemary from the cream and whisk 1 cup of the hot cream mixture into the egg mixture. Pour the tempered eggs and cream mixture back into the pot with the remaining cream and simmer on low for 5-7minutes, frequently stirring with a wooden spoon until the rosemary-infused custard thickens and coats the spoon.
Stir the pear puree, vanilla extract, and almond extract into the custard base, cover the ice cream base with plastic wrap, pressing it directly onto the surface of the custard, and chill it in the refrigerator overnight. Churn the pear ice cream in an icebcream machine according to the manufacturer's directions, then transfer the pear ice cream to an airtight container and freeze for 4-6 hours until the icebcream is set.