For chai tea simple syrup:

• In a small pot bring water, sugar and chai tea bags to a boil. Cook, stirring frequently for 10-12 minutes until sugar is dissolved and liquid has started to reduce. Remove tea bags halfway through cooking to avoid them breaking apart. Remove from heat and cool completely.
• Preheat oven to 350F and line an 8x8 baking pan with parchment paper.
• Heat a small pan over medium heat, toast chopped hazelnuts until aromatic about 3-5 minutes.
• Cream butter, icing sugar and cooled chai tea simple syrup together with a mixer at medium speed until light and fluffy, about 2 minutes. Lightly mix in flour and toasted hazelnuts.
• Add ½ cup of chopped hazelnuts (reserving the rest for sprinkling at the end), and mix with hands until dough begins to clump together.
• Pour dough into prepared pan, it will be loose and crumbly, don't worry! Using your hands, pack it down. Bake for 30-35 minutes or until fully cooked. Remove from oven and allow to cool about 10 minutes, carefully remove from pan to a wire rack and allow to cool completely, about an hour.
• Meanwhile, make the glaze; whisk icing sugar with chai tea simple syrup.
• Once shortbread bars are cool, remove from baking pan, drizzle with chai tea glaze and sprinkle with remaining hazelnuts. Cut into 16 equal squares.