To make romesco coulis, blend or process all ingredients until smooth.
Melt butter in a small saucepan. Add flour. Cook, stirring, until mixture bubbles. Gradually whisk in milk. Cook, stirring, until white sauce boils and thickens. Season with white pepper.
To prepare Tigres, bring wine to boil in a medium saucepan. Add mussels. Cook, covered, for a few minutes until mussels open. Remove from heat.
Remove mussel meat from shells and roughly chop. Reserve ten half-shells.
Add mussel meat to white sauce with prawns, peppers, parsley, garlic and eschallot. Divide mixture among shells.
Dust filled half shells with flour. Dip in egg then panko. Repeat crumbing twice.
Shallow fry until golden brown and crisp. Drain on absorbent paper. Serve with romesco coulis.