Rinse 1 cup of the berries and lay out to dry on a cooling rack.
Cook the other cup of berries in a small saucepan with 1 tsp sugar. Cook and stir over medium heat for about 6-8 minutes, or till berries are mashed and mixture is thick. Cool. (I placed my pan in an ice water bath to speed up the process.)
Mix flour, baking powder, and salt in a large mixing bowl. Gently stir in the rinsed and dry berries.
In another bowl, mix eggs and sugar till thick. Add butter, oil, buttermilk, and vanilla. Fold into dry ingredients.
Fill muffin cups 3/4 full. Spoon about 1 tsp of cooked berries on top of each muffin. Swirl in with a knife.
Combine topping ingredients till crumbly and sprinkle on top of muffins. Bake at 350° for about 18 minutes.