Soba noodles are common in Japanese cooking. The noodles are made of buckwheat flour and are typically served cold or within a broth.
Soba noodles can be found in a variety of flavors including green tea or yam or seaweed. There are also instant, flavored packaged noodles available. You can find these noodles in Japanese or other Asian markets as well as many well-stocked grocery stores including Whole Foods Markets. You can also find them online at Amazon: Soba Noodles Buckwheat.
Chuka soba noodles are not buckwheat soba noodles. In Japanese, "chuka" is the word for Chinese. Chuka soba noodles are the Japanese version of Chinese egg noodles. These slightly yellow-color curly noodles are made simply with wheat flour, water, salt and yellow food coloring. These are the noodles commonly used in Yakisoba noodles.
Soba noodles should be rinsed before you use them. Be sure to do this or you may get sticky noodles. Place the noodles in a large pot of boiling water. The pot should be wide enough for the noodles to fit horizontally. Given them a gentle stir to separate them then allow them to boil for 5-8 minutes. Don't let them overcook.