Preheat the oven to 350 and line the muffin pan cups with cupcake liners.
In a large mixing bowl, mash the strawberries with a fork.
Add sugar, vegetable oil, egg, buttermilk and vanilla. Whisk well until all incorporated.
Add flour, baking powder, baking soda and salt. Whisk until all smooth and combined.
Divide the batter among the muffin cups, filling them 3/4 of the way.
Bake for 18-20 minutes. Cool completely before frosting.
Frosting: (use whisk attachment here) in a bowl of an electric mixer, add the mascarpone cheese, heavy whipping cream and vanilla extract. Start on low to mix the ingredients and gradually increase the speed over a few seconds to medium-high. Do no walk away, this will be ready fast! Slowly pour in the sugar. Beat on medium-high until soft peaks form and gradually lower the speed, over a couple of seconds.
Once the cupcakes are cooled, frost them and top off with diced strawberries.