How many high risks violations did the Tiramisu Kitchen violate?
Tiramisu Kitchen is the name of the business; high risks violations refer to risk_category = 'High Risk';
SELECT COUNT(T1.business_id) FROM violations AS T1 INNER JOIN businesses AS T2 ON T1.business_id = T2.business_id WHERE T2.name = 'Tiramisu Kitchen' AND T1.risk_category = 'High Risk'