Wash, peel, and core the apples, then cut them into ¼-inch thick slices or 1-inch cubes, depending on your presentation preference.
In a medium bowl, combine the flour, oats, brown sugar, cinnamon, and salt. Add the cold cubed butter and use your fingertips to work it into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized pieces remaining. If using nuts, fold them in now.
Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper, spread the crumble mixture evenly, and bake for 15-20 minutes until golden brown, stirring halfway through.
While the crumble bakes, melt the butter in a large skillet over medium heat. Add the sliced apples and cook for 5 minutes, stirring occasionally.
Sprinkle the brown sugar, cinnamon, nutmeg, and cloves over the apples, stirring to coat evenly. Let the sugar melt into the apples for about 2 minutes.
In a small bowl, whisk together the cornstarch and water, then pour this mixture into the skillet. Add the lemon juice and continue cooking for another 3-4 minutes until the sauce thickens and coats the apples with a glossy finish.
For individual servings, divide the warm apple filling among serving dishes. Top generously with the crispy crumble. For a family-style presentation, transfer the apple filling to a shallow serving dish and scatter the crumble over the top.
For the full experience, top each serving with a scoop of vanilla ice cream and a drizzle of caramel sauce. Garnish with fresh mint leaves for a pop of color. Serve immediately while warm.