Beef Pirozhki

Combine warm milk and yeast in the bowl of a stand mixer fitted with the dough hook. Let sit until foamy and bubbly (about 10 minutes). Add flour (reserving a small amount), melted butter, egg, sugar, and kosher salt. Knead until dough is soft and supple.

Turn dough out onto your work surface. Grease the bowl with oil; place dough back in bowl. Cover and let rise in a warm place until doubled in volume (about 1 hour).

Meanwhile, heat olive oil and butter in a pot over medium-high heat. Add ground beef, onion, and garlic; season with kosher salt and black pepper. Cook, breaking apart beef with a wooden spoon, until no longer pink (5 to 7 minutes); continue cooking, stirring occasionally, until evenly browned (about 2 minutes more). Remove from heat.

Stir dill into beef mixture. Add chicken broth, stirring to scrape up browned bits from the bottom of the pot. Cool mixture for 10 minutes; stir in Cheddar cheese and Parmesan cheese. Cool filling completely.

Transfer dough to a work surface; punch down to release air bubbles. Pinch off a piece of dough; form into a ball, then press into a disk. Lightly dust with flour; roll into a circle about 1/8-inch thick and 5- to 6-inches in diameter. Dampen edges of dough circle with water.

Place dough circle in one hand; add about 3 tablespoons beef filling. Pinch dough edges together to seal. Place pirozhki on the work surface, seam-side up; pinch off any excess dough. Moisten center of seam with water. Fold 2 ends inward and flip pirozhki over, seam-side down; press down lightly.

Form remaining pirozhki using remaining dough and filling; rest until dough rises slightly (15 to 20 minutes).

Heat oil in a deep fryer or large saucepan to 375 degrees F (190 degrees C). Fry pirozhki in batches, seam-sides down, until golden brown (about 90 seconds). Flip and fry until browned on the other side (about 90 seconds more). Drain on paper towels. Cool for about 3 minutes.