In a medium bowl, whisk together the flour, baking powder, and salt. In a large bowl, mix together egg and sugar until thick and well-blended. Gradually stir in the oil until blended, and then blend in the sour cream. Slowly mix half of the flour mixture into the wet ingredients, blend in milk, and then stir in remaining flour mixture until just combined. (Add a splash more milk if batter is too thick, but be careful not to add too much!) Gently fold 1½ cups of diced strawberries into the batter.