In a small saucepan, gently boil the peas for about 5 minutes.
Meanwhile, heat a large, flat saucepan over medium. Add oil and heat through, then add shallots and cook until aromatic.
Drain peas and add to shallots. Stir in broth, wine, and lemon juice, reduce heat to medium-low, and cover. Cook for about 8 minutes, stirring occassionally and making sure the liquid has not completely evaporated. (If it has, add more broth.) Salt and pepper to taste. Add spinach and re-cover pan.
In the meantime, heat a frying pan to medium and add pork belly. Cook for about 5 minutes on each side, until fat starts to firm up and get a crisp edge. Remove from heat.
Once spinach has wilted and the liquid is mostly gone, stir in butter until melted.
To serve, pour peas into two bowls and lay two slices of pork belly on each.