Whenever I bake Nigella's Chocolate Chip Cookies they always spread out and eventually join together by the end of cooking. It also happens with other cookies, even ones roll and I cut out in shapes. What am I doing wrong?
All cookies will spread slightly and for Nigella's Chocolate Chip Cookies (from Kitchen) make sure that you are spacing the cookies out sufficiently on the baking sheet so that if they do spread slightly then they still won't touch each other.
However if you are having a problem with several different cookie recipes then there could be a few reasons for the cookies spreading. The most likely reasons are that the cookie dough is too warm when it goes into the oven or the oven temperature is too low. If the dough is too warm when the cookies go into the oven then the fat in the dough will melt quickly and this will cause spreading. This can be a particular problem if you live in a warm country. We would suggest shaping the cookies, putting them on a baking sheet and then chilling them for 20-30 minutes before baking (you can preheat the oven as the cookies chill). Also check your oven temperature, preferably with an oven thermometer, as some ovens can run a little cool and this again will cause the fat to melt out before the rest of the cookie has set.
There is also a chance that the butter and sugar in the recipes are being beaten too much. Beating adds air and the bubbles of air will expand in the hot oven, causing spreading. Beat the butter and sugar until just combined and smooth, unless the recipe particularly specifies otherwise.