1 stick (8 tablespoons) unsalted butter, at room temperature
1/4 cup honey
1 tablespoon pure vanilla extract
1 large egg, at room temperature
2/3 cup raisins
Puree 3/4 cup of the oats in a blender, starting on low speed and gradually increasing to high, until ground to a fine powder. Add the dates, 1/4 teaspoon salt and 2 cups cold water and puree until smooth, thick and creamy. Add the condensed milk and puree until combined. Transfer to a large bowl.
Whip the cream and granulated sugar in a bowl with an electric mixer until stiff peaks form. Fold one-third of the whipped cream into the oat milk mixture until combined and lightened. Fold in the remaining cream until completely combined. Transfer the mixture to a 9-by-13-inch pan, wrap tightly with plastic wrap and freeze until firm but malleable, about 3 hours; you want the ice cream to hold its shape but be able to be flattened between 2 cookies without breaking them.
Arrange an oven rack in the center of the oven and preheat to 375 degrees F. Line a rimmed baking sheet with parchment.
Whisk together the flour, cinnamon, salt and soda in a small bowl until combined. Beat the brown sugar and butter in a large bowl with an electric mixer on medium-high speed until light and fluffy, about 3 minutes. Add the honey, vanilla and egg and beat on high until creamy, about 3 minutes more. Add the flour mixture and mix on low until combined. Add the remaining 1 3/4 cups oats and beat on low until combined. Fold in the raisins.
Arrange twelve 1-ounce scoops (1 1/2-tablespoon portions) of cookie dough on the prepared baking sheet, leaving about 2 inches between each. Bake until the cookies have spread and are deep golden brown, 9 to 11 minutes. Cool on the sheet for 10 minutes, then transfer to a rack to cool completely. Let the baking sheet cool slightly, then continue with the remaining cookie dough.
When ready to assemble. Scoop 1/3 cup of ice cream and sandwich between 2 cookies; repeat with the remaining ice cream and cookies. Transfer the sandwiches to a rimmed baking sheet, wrap in plastic wrap and freeze for at least another 8 hours before serving.