Hong Kong–Style Stuffed French Toast

Name: Hong Kong–Style Stuffed French Toast
Ingredients: 1/4 cup creamy peanut butter; 8 slices milk bread or brioche (3/4 inch thick), slightly stale; Canola oil, for frying; 1 cup half-and-half; 4 large eggs; 1 tablespoon granulated sugar; 1 teaspoon vanilla extract; 1/4 teaspoon ground cinnamon; 1/4 teaspoon kosher salt; 3/4 cup sweetened condensed milk; 1/4 cup whole buttermilk or half-and-half, plus more as needed; 1 teaspoon grated lemon zest plus 2 tablespoons fresh lemon juice; Softened unsalted butter and flaky sea salt, for serving; Lap cheong crumble, for serving (optional)