Peel carrots and discard dry ends. Chop into 1⁄2-inch pieces and place in pot with cashews and stock. Turn heat to high and bring to boil. Reduce heat to medium and cook until carrots are cooked through (about 10 minutes).
Remove from heat and, using slotted spoon, scoop carrots and cashews into food processor. In separate bowl, measure out 1⁄4 cup of cooking liquid and dissolve miso in it. Add to bowl with carrots and process until smooth. Serve topped with sesame seeds, or refrigerate in airtight container for up to 4 days.