How do I apply the interface concept with the base-class in design?

Question

I am now studying the concept of OOD and I have created a program for a pizza shop. The base class here is pizza. I want to put a spicy characteristic for pizza as an interface, but I find a problem in the actual application. Here is the code. How can I combine making pizza with it being spicy?

how i can make beef spicy pizza object [how can i make pizza and make it spicy via interface]

how to use interface here.

#include <iostream>
#include <string>
using namespace std;

// base-class
class Pizza
{
private:
    void MakeDough()
    {
        cout << "Make " << getPizzaType() << " Pizza Dough is Done.." << endl;
    }
    void Bake()
    {
        cout << "Bake " << getPizzaType() << " Pizza is Done.." << endl;
    }
    void AddToppings()
    {
        cout << "Adding " << PizzaToppings() << " is Done.." << endl;
    }

protected:
    virtual string getPizzaType() = 0;
    virtual string PizzaToppings() = 0;

public:
    void MakePizza()
    {
        MakeDough();
        AddToppings();
        Bake();
        cout << "======================================\n";
        cout << getPizzaType() << " Pizza is Done..\n" << endl;
    }
};


//interface
class Spicy
{
public:
    virtual void makePizzaSpicy() = 0;
};


class BeefPizza : public Pizza, public Spicy
{
protected:
    // from Pizza Class
    virtual string getPizzaType()
    {
        return "Beef";
    }
    virtual string PizzaToppings()
    {
        return "Beef Pizza Toppings";
    }

public:
    // from spicy class
    virtual void makePizzaSpicy()
    {
        // code
    }
};

class ChickenPizza : public Pizza
{
protected:
    virtual string getPizzaType()
    {
        return "Chicken";
    }
    virtual string PizzaToppings()
    {
        return "Chicken Pizza Toppings";
    }
};

class MakingPizza
{
public:
    void MakePizza(Pizza* pizza)
    {
        pizza->MakePizza();
    }
};


int main()
{
    // here how i can make beef spicy pizza object
}