Split pea and ham soup with ham and cheddar toasties

Ingredients

• 40 gram butter, coarsely chopped
• 2 onions, finely chopped
• 1 fennel bulb, finely chopped
• 4 clove garlic, finely chopped
• 1 ham hock (about 1.2kg)
• 2 1/4 cup (500g) dried green split peas
• 3 cup frozen baby green peas
• 1 cup (firmly packed) baby spinach
• 1/2 cup (firmly packed) flat-leaf parsley
• 1/2 cup (firmly packed) mint, plus extra to serve
• finely grated rind and juice 1/2 lemon, or to taste
• Ham and cheddar toasties
• softened butter, for spreading
• 8 slice white bread (use gluten-free if required)
• dijon mustard*, to taste
• 1/2 cup grated vintage cheddar