Your butter needs to be “room temperature”, or around 65ºF. If it is too cold, it won't blend with the sugar evenly and will be almost impossible to beat it into a smooth consistency; if it is too hot, the butter won't be able to hold the air pockets that you are trying to beat into it.
Too cold, and you'll end up with a chunky, gritty mixture. Too soft or melted, and you'll end up with a greasy, deflated puddle. Cream until your mixture looks smooth, very pale yellow, and has noticeably increased in volume. If you don't cream for long enough, your mixture will appear gritty, yellow, and flat.
The best results come from beating the ingredients together until the mixture is pale in color and fluffy—how long this takes depends on the strength and speed of your mixer. In some cases, the step will take about 5-7 minutes, but more powerful mixers may only take 2 or 3.
The temperature of your butter is one of the most important factors in properly creaming butter and sugar. It must be at a COOL room temperature, about 67°F. If your butter is visibly greasy and your finger sinks into the stick when pressed, it's far too warm.
It is possible to overmix the butter and sugar. If you overmix, however, the butter will separate out of the mixture and it will be grainy and soupy, so be sure to stop once your butter becomes light and fluffy.
It is possible to over-cream butter and sugar. If creamed too long the mixture will turn white and, if you use it, will give your baked goods a dense, almost gluey, texture. So, don't leave your mixer unattended and keep an eye on the mixture so you can see when it's ready.
First of all, the butter should become light and fluffy – it will feel lighter when you scrape it with a spatula or pick the beaters up out of the bowl. The color should turn a light pale yellow color and the total volume of what you're beating will increase in volume – that's the air you're beating into it.
(a) traditional cake mixing method where sugar and fat are beaten until light and fluffy, after which egg is added in several small portions before the rest of the liquid and flour are added slowly to prevent curdling.
With your wooden spoon,stir the butter and sugar(s) until they are light and fluffy. Use a rubber spatula to scrape the mixture off the sides of the bowl periodically. The butter is "creamed" when it has almost doubled in mass and it has lightened to a yellowish-white color.
Sometimes separated toffee or caramel can be saved by removing the saucepan from the heat and stirring constantly until it comes back together into a smooth mixture. Gradually return it to the heat, stirring constantly. You can also try adding a spoonful or two of very hot water to the toffee to help it come together.
One way to fix broken cake batter is to add a bit of flour, one tablespoon at a time, until it smooths out again. The flour helps the liquid and fat come back together and creates a smooth, lump-free mixture.
Not sure how long to soften butter? Keep an eye on it, but the easiest way to soften butter is to remove a cold stick from the refrigerator and let it hang out at room temperature for 30 to 60 minutes until it becomes room temperature or until just spreadable.
Add Sour Cream
To help prevent a dry, dense cake, let's add a creamy and light wet ingredient. Milk is usually required in a cake recipe to thin out the batter and lighten up the crumb, but sour cream is often overlooked. In addition to milk, add a Tablespoon or 2 of sour cream.
It should be soft enough that your finger will make an imprint with zero resistance, but not so warm that the butter looks shiny or greasy (or is melted completely, which happens around 90°F).
Starting with your stand mixer or hand mixer on medium speed, beat the butter and sugar until it is pale yellow, light, fluffy, and has visible volume, using your spatula to scrape down the sides of the bowl as needed.
You can blend more but only ever half fill the jug or you might have some trouble getting it to churn without overheating. If your whipped cream turns to liquid, it has overheated in the blender. It's not wasted.
Why care about when to stop churning? If churning ceases too soon, much fat is lost to the buttermilk. If over-churned, the butter will contain too much buttermilk and be very difficult to wash clean.
Another tip, if the sugar and butter mixture appears slightly curdled, the butter was likely too warm or was beaten for too long.