Preheat oven to 300 degrees F (150 degrees C). Place the cream cheese, sugar, and flour in a mixing bowl and cream until light and fluffy. Beat in eggs one at a time, mixing well after each addition. Scrape bowl.
Melt 4 ounces of the white chocolate. With an electric mixer on low speed, mix melted white chocolate into cream cheese mixture. Keeping electric mixer on low, slowly beat in the vanilla and 1/2 cup of heavy cream. Blend well. Mix in caviar. Pour in cupcake wrapper.
Bake at 300 degrees F (150 degrees C) for about 20 minutes, or until center of the cheesecake is just firm. Cool at room temperature for 30 min. Refrigerate until set prior to frosting.
In a large bowl, using a handheld electric mixer, beat the butter at medium speed until creamy. Beat in the melted white chocolate. Add the confectioners' sugar and vanilla and beat at low speed, scraping the sides and bottom of the bowl, until light and fluffy. Mix in caviar.
I had trouble piping this frosting because the white chocolate either a) solidified really quickly and gunked up the tip or b) was not fully melted in the first place. I ended up just spreading it and using a toothpick to swirl the caviar around.