• Preheat the oven to 210°C. Prepare a muffin tin and paper cups.
• Add a little bit of butter to the deep pan and add fresh strawberries / frozen strawberries. Cook them until they are very soft and press them down until they have a consistency of puree. Don't do this if you're already using a strawberry puree.
• In a bowl whisk butter with sugars until fluffy. It can take 4 minutes or even more. Then add oil with sour cream and whisk again until it gets creamy.
• Add strawberry puree and mix well. Add eggs and whisk until well combined.
• Add flour and baking powder and whisk until the flour disappears. Do not over-mix!
• Fill the paper cup until it's full and bake for 5 minutes. Then decrease the temperature to 180°C and bake for 8-12 minutes (I baked mine for 10 minutes). Take the cupcakes out of the oven and let them rest in the muffin tin for another 10 minutes. Then take them out of the baking tin. Let cool completely.

Strawberry frosting

• Do the same with strawberries to get a strawberry puree.
• In a bowl whisk butter, icing sugar, and strawberry puree until it has a consistency of frosting. Add more icing sugar if needed.