What is the best way to sew chenille to a cotton or flannel piece of fabric?

I sewed a blanket for my daughter using flannel and chenille. I laid the chenille flat on the floor and placed the flannel over top. Then I pinned the two pieces together, sewed a 1/2" seam, flipped it right-side out, and top-stitched. Then I washed it, and it was perfect!! No extra flannel or chenille. I washed it a second time, and now there is a ton of extra chenille. What can I do with future blankets to avoid this? I also have tons of burp cloths this same way with absolutely no problems. Any advice is welcome. Thanks in advance!!