Preheat oven to 350. Butter a 10" springform pan and line the bottom with parchment paper.

In a stand mixer or using an electric mixer, cream together butter and sugar on medium speed until fluffy, about 5 minutes.

Scrape down bowl and add vanilla and eggs, 1 at a time, beating for 20 seconds, after each addition. Scrape down the bowl.

In a large measurung cup whisk together the flour, baking powder and soda, and salt. Add to butter mixture in thirds, alternating with the sour cream. Beat for 45 seconds after each addition and begin and end with the flour mixture. Spread the batter evenly in the prepared pan.

Wipe out the mixing bowl and use this for the cream cheese mixture.

Cheese Filling:

Put the mascarpone or cream cheese in a bowl and beat until smooth, 2 -3 minutes on medium speed. Add the egg and vanilla and beat until well blended. Pour or spread the cheese mixture over the batter in the pan, leaving a 1" border around the outside.

If your jam is pourable, pour evenly and spread over the cheese layer. You may need to heat it briefly in the microwave.

Streusel Topping:

In a small bowl whisk the flour, sugar and salt. Add the nuts and stir to combine. Stir in the butter until the dry ingredients are moistened. Sprinkle evenly over the jam layer.

Bake 55-60 minutes, until the top is golden. The center may still be a touch jiggly. Remove to a wire rack and let cool for 1 hour in the pan.

White Chocolate Drizzle: (optional)

Heat the chocolate with the cream on high in a microwave oven for 30 second intervals. White chocolate burns quick so do not overdue it.  Whisk  between each interval until mixture is smooth. Crumble fine dried strawberries into the glaze and stir well. This adds color and flavor but is optional.

Assembly: Run a thin knife around the sides of the pan. Remove the sides. Place on a serving plate and drizzle with white chocolate drizzle or sprinkle with powdered sugar. Or not.