Brewing Turkish coffee is a lovely ritual, and it is completely normal to experience boil-overs when you are first relearning the technique. The secret lies in managing headspace, burner size, and heat velocity.
First, make sure you are using cold water and filling your cezve only up to the narrowest point of its neck. That narrow waist is specifically designed to concentrate the rising foam, but you need at least an inch of empty headspace above it to give the foam room to swell without spilling over.
Second, place your cezve on your smallest burner set to low or medium-low heat. Stir the cold water, finely powdered coffee, and optional sugar thoroughly before putting the pot on the stove, but do not stir it once it is over the flame. A proper brew should take about two and a half to three minutes. If the coffee heats too quickly, the steam bubbles expand aggressively and cause an uncontrollable eruption.
Finally, stay right by the stove as the coffee approaches a simmer. You will see a rich, dark foam develop around the edges and slowly creep toward the center, lifting the surface. The moment this dome begins to rise steadily up the neck, smoothly lift the cezve an inch or two off the heat source. This drops the temperature immediately and halts the rise without collapsing the foam. You can gently spoon some foam into your demitasse cup, place the cezve back onto the low heat for a few seconds to let it rise gently one more time, and then pour slowly down the inside wall of the cup.
