Fragrant warming spices flavor this ice cream inspired by the spiced tea of Indian origin.
Combine coriander, peppercorns, allspice, cloves, cardamom, and cinnamon in a small skillet over medium-high. Cook, swirling pan frequently, until fragrant, 2 to 3 minutes. Combine toasted spices, milk, ginger, and salt in a medium saucepan. Bring to just under a boil, then remove from heat and let stand 45 minutes. Return to a simmer; add tea. Remove from heat; let steep 10 minutes. Strain through a cheesecloth-lined sieve (you should have about 2 cups; if not, add more milk); discard solids.
Prepare a large ice bath. Return mixture to saucepan and add 1/2 cup sugar; bring to a simmer. In a large bowl, whisk remaining 1/2 cup sugar into egg yolks. Gradually whisk in half of milk mixture. Pour back into pan and cook over medium, stirring constantly, until mixture is thick enough to coat the back of a wooden spoon, 5 to 6 minutes. Pour custard through a fine-mesh sieve into a bowl. Add heavy cream. Place in ice bath. Let chill, stirring occasionally, at least 30 minutes. Refrigerate until very cold, at least 2 hours and up to 2 days.
Freeze custard in an ice cream maker according to manufacturer's instructions. Serve ice cream soft from machine, or freeze in an airtight container up to 2 weeks. If frozen for more than 4 hours, let ice cream stand at room temperature 10 to 15 minutes before serving.