Special equipment: a 9-by-5-by-3-inch metal loaf pan, chilled
Whisk together the condensed milk, matcha powder, vanilla and salt in a large bowl and set aside.
Whip the cream with an electric mixer on medium-high speed until firm peaks form, about 2 minutes. Fold about 1/2 cup of the whipped cream into the condensed milk mixture with a rubber spatula until combined, and then fold the lightened mixture into the whipped cream until well blended. Pour into a chilled 9-by-5-by-3-inch metal loaf pan, cover with plastic wrap and freeze until solid and scoopable, about 3 hours or up to overnight.
Preheat an oven to 300 degrees F and line a baking sheet with parchment paper.
Arrange both the bottoms and tops of the buns cut-side-down on the prepared baking sheet and brush their tops with the egg white, then sprinkle the sugar and sesame seeds on the top buns and only sugar on the bottom buns. Bake until the tops are no longer glossy and the buns are just slightly toasted, about 5 minutes. Set aside to cool completely.
Spread 1/4 teaspoon raspberry jam on the cut-side of each bun half. Scoop 1/4 cup of the ice cream onto each of the bottom buns, then sandwich with the remaining tops. Wrap and freeze until ready to serve, at least 30 minutes. The sandwiches can be frozen for up to 3 days.
Copyright 2015 Television Food Network, G.P. All rights reserved.