In small measure, stir orange blossom water with 1/3 cup water. Refrigerate for 5 minutes.
In large bowl, whisk together all-purpose flour, semolina, granulated sugar and salt. Using pastry blender or 2 knives, cut in butter until mixture resembles fine bread crumbs; drizzle orange blossom water over flour mixture, stirring briskly with fork until dough holds together. Form into ball; press into disc. Wrap in plastic wrap and refrigerate until firm, about 15 minutes. (Make-ahead: Refrigerate for up to 3 days.)
Meanwhile, in saucepan over medium-high heat, bring dates and 1 cup water to boil. Reduce heat and simmer until thickened and smooth, about 5 minutes. Let cool.
Drop dough by 2 tbsp onto waxed paper–lined baking sheet to make 26 mounds. Roll each into ball. Place 1 ball in palm of hand; press thumb halfway into centre of ball, forming cup shape to hold filling. Spoon in 1 tsp filling; fold dough over filling and pinch edges to seal. Repeat with remaining balls and filling. Place, pinched side down and about 1 inch apart, on parchment paper–lined or greased rimless baking sheet. Refrigerate until firm, about 15 minutes. (Make-ahead: Cover and refrigerate for up to 2 days.)
Bake in centre of 400°F oven until bottoms are golden brown, 20 to 25 minutes. Transfer to rack. Dust with icing sugar. (Make-ahead: Layer between waxed paper in airtight container and store at room temperature for up to 4 days or freeze for up to 2 weeks; after thawing, dust again with icing sugar.)