I wait all spring for iced-coffee season to start in earnest. While I like it pretty much any way, including black on the rocks, the pinnacle of iced-coffee treats has got to be the Vietnamese way: strong and spiked with sweetened condensed milk. I don’t have any of the little coffee filters they present you with in Vietnamese restaurants, but recently when I was entertaining a crowd on a hot summer morning, I made up four pots of extra-strong coffee, mixed them with two cans of good old Eagle Brand and chilled the whole mixture. I’d bought one of those big ridged, blue-glass jars they often keep aguas frescas in at Mexican restaurants, at East Bay Restaurant Supply. “Making sangria?” the guy at the checkout asked me. “No, coffee,” I replied. I got a funny look then, but when the jar was filled up with ice and my highly caffeinated cold brew, it seemed to please the guests.