Collect the cream of your homemade yoghurt. You can use some of your fresh cow's milk's cream to add to it too. Once you have enough to work with (perhaps about 300g-500g), mix it well with a blender for a few minutes. If it melts too much while going through the blender, add some cold water.Take out the hardened bits of the cream. Put it under cold water a few times (as if washing it a few times). This procedure also helps with it to form a more solid texture.
Add some salt and mix it. If you are planning to use this butter as a spread, you can choose not to add salt to it. However, if you are going to leave it in your fridge and use it in your cooked meals, you can add salt (about a teaspoonful).
ricotta cheese making. Add some salt to it and bring it to boil. Simmer for a while and take the cheese/the solid textured product out and put it in a strainer. When drained and cold, place it in the fridge. You can use your homemade ricotta cheese in omelette or as a pastry filling.