Chicken, avocado and cheese melts

Name: Chicken, avocado and cheese melts
Prep time: 20 min
Cook time: 15 min
Total time: 35 min
Cuisine: European, British
Ingredients: 4 single chicken breast fillets, trimmed; Olive oil spray; Salt & freshly ground pepper; 2 ripe avocados, peeled and stone removed; 4 tbsp spreadable cream cheese, at room temperature; 4 shallots, finely chopped; 2 ripe tomatoes, finely chopped; 1 1/2 tbsp fresh lemon juice; 8 slices Italian-style bread; 8 slices Colby cheese, halved; 120g snow pea sprouts, trimmed, optional